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Classic Bike Trackdays

PE250B Vintage Supermotard

 
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James P



Joined: 31 Mar 2013
Posts: 156
Location: Sydney, Australia

PostPosted: Tue Dec 24, 2019 7:12 am    Post subject: PE250B Vintage Supermotard Reply with quote

I think that the PE250B appeared some time during 1976, whereas 'supermotard' as we know it didn't appear until 1979 (with the American television series Superbikers). However, I am hoping for some leeway through artistic licence or some similar facility!

This is what a standard PE250B looks like:


Here are a few photos of my PE250B:











Some details will follow.


Regards,
James
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James P



Joined: 31 Mar 2013
Posts: 156
Location: Sydney, Australia

PostPosted: Tue Dec 24, 2019 7:24 am    Post subject: Reply with quote

In 2004, I was looking for another project (who knows why – I had plenty of them already) and wanted to build a ‘vintage supermotard’ kind of bike.

I originally looked around for a later model PE250 or PE400, knowing that the engines are interchangeable for the later models. I even went as far as buying a couple of PE400 engines and assorted parts with the intention of fitting a 400 engine into a 250 (if I couldn’t find a complete 400). The few complete PE250s on offer at that time were not really what I wanted (worn out and/or too many parts missing), so I investigated more deeply when I saw this early PE250B for sale.
When I looked at the bike in November 2004, it had been functionally rebuilt by the owner for use in vintage enduro events. He had taken some trouble during the rebuild with not too many corners cut (e.g. fasteners painted silver instead of being replated, non-original rear mudguard and various other small bits and pieces) and it seemed that all ‘errors’ should be reasonably easily fixed. Thankfully, the bike came with some of its rare original parts in a box, such as the headlight assembly and speedo.
I was generally impressed with the condition of the bike, so a deal was done. As a result of buying this bike (and not a later one), my plans changed somewhat. I had originally intended to fit a disc-brake front end and other more modern parts, but thought it would be a shame to spoil such an early example if I could get hold of the missing original parts. As such, my amended intention became to convert the bike into a ‘road bike’ without disturbing its fairly original appearance too much.
A quick test ride before buying tempted me to leave the engine alone. However, I’m glad I didn’t as I later found the primary drive nut loose on the end of the crankshaft when dismantling!

This what the bike looked like when I bought it in 2004 (photos by previous owner):




One of the most difficult parts to find was an original tail light assembly - none of the modern ones looked right. I did manage to get a few original NOS parts at reasonable prices from Bruce Northcott in Blacktown, who had set up a Suzuki dealership there in the 1960s. His vaults included a PE250C tail light assembly (looks the same as B model, but has no brake light globe) and a box of spare lenses. I was later lucky enough to get a job lot of parts from the USA from someone who had dismantled a PE250B, which included a restorable tail light assembly (missing the lens, but I already had a box of those by that time!).

The initial rebuild took about 18 months – the only things I didn’t dismantle were the forks (but they got new oil) and the wheels.
I soon found that the forks which came with the bike were not the originals. Some detective work revealed that they were from a YZ125D or IT175D. Unfortunately they were a bit too long, with little room to push the stanchions up through the yokes before they hit the handlebars. I decided to just use them and keep my eyes open for a more suitable set.
With my original ‘vintage supermotard’ plan, I would have liked to have built or bought a new set of wheels just for road use. However, the wheels on the bike had already been rebuilt for the previous owner using the original hubs and rims with new spokes, so I couldn’t really justify the expenditure on new wheels at that time. I just bought some Avon Distanzia dual-purpose tyres in standard sizes (90/90-21 front and 120/80-18 rear) for the standard wheels.

The bike was on the road in June 2006 and I rode it for about 150km to set it up. The Barnett clutch kit I had fitted was plagued by drag (despite soaking the plates in oil for several months beforehand), which made the bike a real pain to ride in slow traffic. I eventually (much later) discovered that the plate stack was a little over 0.5mm taller than the stack of standard plates, which may explain the problem. At that point in time I wasn’t sure what to do about the clutch, so concentrated on other aspects of the set-up...principally the exhaust.
The original exhaust came with the bike, but had a large crease in the header pipe and the original silencer was missing (the previous owner had just stuck an RM80/100/125 short silencer on the end of the tailpipe, which reduced the inside diameter a fair bit). When looking around for a replacement exhaust, I settled on a Circle-F system from the USA which was made especially for the early PE250 models. The Circle-F exhaust system came with two different silencers – loud and louder! I spent ages trying all sorts of things to quieten it down, but to little effect. At that time, I ended up with the main part of the expansion chamber wrapped and I modified an FMF Turbine Core silencer to fit. The FMF silencer did make a difference, but it was heavy and obtrusive…and the bike was still too loud.
Although everything else about the bike seemed OK, I put it to one side on account of the clutch and exhaust difficulties. I kept it road-registered until mid 2010, when I decided that it was costing too much for a bike which I hardly ever rode and still needed more work. Other projects with more certain prospects were brought to the fore, so the PE was laid up. I considered trying to sell it on several occasions, but I regained some enthusiasm for it in 2017 after seeing a friend’s collection of Yamaha IT models, slightly modified for flat-track racing.
I thus decided to have another go at the PE. I wanted to make it look more like a flat-tracker, hill-climber and/or supermotard bike, but without spoiling its fairly original appearance. Proper road tyres with wider wheels (and smaller diameter front) would be essential, but so would be fixing the clutch and making the exhaust quieter!
By that time, I had already found a set of decent forks from a PE250C or N model – not identical to the B model forks, but with practically the same dimensions. Upon reconditioning these and fitting them, the front end was somewhat lower than before.

This is how it looked when I first got it on the road in 2006 (notice makeshift chain guard - the standard bike didn't have one):



More details to follow.


Regards,
James
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James P



Joined: 31 Mar 2013
Posts: 156
Location: Sydney, Australia

PostPosted: Tue Dec 24, 2019 7:33 am    Post subject: Reply with quote

This is the bike in 2009 with the FMF Turbine Core silencer:



Although the Barnett clutch kit could probably have been made to work better by modifying the bike’s clutch basket, hub and/or pressure plate, I just decided to refit the original plates (thicknesses still within specification) with new genuine standard springs. What a revelation - the clutch is now much better and riding in traffic shouldn’t be such a pain.

The exhaust would be a little more difficult to sort out, but I was going to try.
The research of Gordon Jennings showed that an ‘internal stinger’ arranged along the lines of his findings should have no effect on the performance, but should reduce noise appreciably. This does however rely on the stinger length being kept the same, which would be difficult on the PE if a silencer was also to be fitted in the original position. With some calculation, I worked out that a larger diameter stinger of longer length would produce about the same back-pressure as the Circle-F pipe’s original stinger and allow a silencer to be fitted in the same position. With this and a basic design in mind, I approached an Australian sheet-metal-worker who has made pipes for many motocross and enduro bikes. He was a little sceptical of the internal stinger concept, but agreed in principle to build me a pipe when his workload allowed it.
For whatever reason, the pipe-builder went cold on the idea (I can only presume, as my attempts to contact him about it went unanswered). I would therefore have to do something myself to modify the existing Circle-F pipe.
I could have modified the pipe with an internal stinger, but I decided that my beginner-level TIG welding skills may be a bit stretched with some aspects of the arrangement. I thus decided to use the ‘side-bleed’ system. This has basically the same effect as an internal stinger (in that the gases are bled from the point of lowest pressure), but can allow the stinger to be kept shorter if the silencer can be accommodated in a suitable position on the bike. I had used the side-bleed system on another project bike to good effect, so thought it would be worth a go on the PE once I found a suitable spot for the silencer.
The result is as seen in the photos. I have fitted a secondhand SP Tadao carbon fibre silencer which I got fairly cheaply from Japan (originally made for a Honda NSR150 I think), using a mounting system I fabricated. This assembly is much lighter than the FMF silencer. I have run the bike once since finishing the exhaust modifications and it does seem much less noisy than I remember…although I’d still like it to be a little quieter. I may try rewrapping the expansion chamber section again to see if it makes any difference. I am however mindful that air-cooled cylinders are always going to be noisier than liquid-cooled ones.

Here is the bike in 2014, still with the YZ/IT forks fitted:



Here it is again about two years later, after I fitted the PE250C/N forks:





One thing I wanted to fit to the ‘updated’ bike was a crash bar, which I intend should protect the engine cases and exhaust in the (hopefully unlikely) event of the bike sliding along the road. I had already started fabricating one around 2009, but didn’t finish it before the bike was laid up in 2010. Keeping the original design, I have now effectively finished it. It is a two-part assembly which slots together from each side, each half having front and rear mounting tabs which are secured to the frame using the engine mount bolts. I also made some sacrificial plastic ‘knobs’ to go on the ends.

This is the crash bar ready for final fitting:





More details and photos to follow.


Regards,
James
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James P



Joined: 31 Mar 2013
Posts: 156
Location: Sydney, Australia

PostPosted: Tue Dec 24, 2019 7:46 am    Post subject: Reply with quote

For the new ‘road’ wheels, I selected a pair of secondhand DR500 hubs and also bought some new stainless steel spokes and Takasago Excel 18” rims (2.15” front and 2.5” rear). The tyres are Bridgestone BT45; 100/80 front and 120/80 rear. I wanted the wheels to look ‘in keeping’ with the age and semi-originality of the bike, so no super-wide rims and tyres as fitted to modern supermotard machines.
The DR rear hub incorporates a cush-drive assembly which is better for a road bike than a direct-solid-mounted sprocket. The width of the rear hub matches the PE swing arm – I just needed to make some bushes for the swing arm slots to use the DR chain adjuster assemblies.

This was the DR500 rear hub after I bought it and removed it from its original rim. Very cruddy, but the price was right:


It was starting to look better after dismantling and cleaning:


Here it is with the front hub after paint stripper:



For the supply of new rims and spokes, I contacted two firms; one in USA and one in UK. Each firm offered spokes at about the same price, but the UK firm was quite a bit cheaper for the same rims.
On this aspect of the project, I ended up quite dissatisfied with the UK firm that supplied the rims and spokes. Its advertising blurb boasted of unrivalled expertise in the field of wheel building and I was initially impressed upon making enquiries. However, on actually committing to purchase, I was told that the firm would supply the rims drilled to suit the DR hubs, but would not calculate the spoke lengths – I had to do this myself. Despite me attempting to (tactfully, I thought) enquire why the firm couldn’t do this for me, it flatly refused without giving anything more than a vague reason. Therefore, I had to get the firm to send me the rims first, so I could measure them for my spoke length calculations. The spoke nipples were also sent with the rims, with only the spokes themselves remaining to be manufactured after I advised of the lengths.
The spokes were duly manufactured to my dimensions and sent by air mail. However, on attempting to fit the nipples to the spokes, I found that they were so loose that the threads barely engaged. I notified the supplier, which sent another set of nipples...which were also too loose! Eventually, the third set of nipples achieved a decent fit and I built the wheels. Thankfully, the spoke lengths were all correct and I needed to grind the ends of only two or three spokes (which I put down to elongated holes in the hubs).
I understood that the firm in USA would have calculated the spoke lengths for me, which may have resulted in less hassle in the end.

The DR500 rear brake assembly is ‘floating’ (i.e. the torque arm is anchored to the frame rather than to the swing arm like the original PE set-up), so I made a new brake pedal boss (a copy of an American-made conversion kit from the late 1970s) to provide a front anchor point for the DR torque arm. The floating system is reckoned to be better, but I doubt I’ll notice any difference – it was still an interesting engineering exercise.
The DR front hub is near identical to the PE one, but using it just allowed me to keep the original front wheel intact. However, now that the front wheel is smaller diameter, the standard speedo drive gear ratio is all wrong. Luckily I found a speedo drive gear assembly from another model which corrects this.

The new wheels after building and getting the new tyres fitted:





The bushes for the swing arm axle slots:


The standard PE rear axle is the same diameter as the DR500 one, but the PE has threaded sleeves which stay in position when the wheel is removed. This may assist with quick wheel changes in competition events, but is rather too complicated for my liking on a bike whose rear wheel (I hope) will hardly ever be removed!

More photos and details to follow.


Regards,
James
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James P



Joined: 31 Mar 2013
Posts: 156
Location: Sydney, Australia

PostPosted: Tue Dec 24, 2019 8:03 am    Post subject: Reply with quote

As the design of the standard PE top steering yoke prevented the front end from being lowered sufficiently (fork stanchions hit handlebars if pushed through only slightly) I decided to try to find an alternative top yoke with swept-back handlebar clamps.
Luckily, there are several contemporary Suzuki off-road bikes with the same fork stanchion diameter and steering offset as the PE – some of them have back-swept handlebar clamps. The best bet (at the time) seemed to be a top yoke from RM125-400C models. These of course have back-swept handlebar clamps, which allow the fork stanchions to be pushed up through the yokes to lower the ride height at the front. I didn’t need as much lowering as I initially thought, as I had already replaced the previous YZ/IT forks with PE250C/N forks, which are slightly shorter…and the 18” front wheel drops the front end a bit as well. The forks still protrude through the top yoke by about 20mm, but I’ll see how it goes on the road with the new set-up before deciding whether any further adjustments are necessary.

The RM125-400C steering yoke assembly:


I have since found that a DR250 top yoke provides the same result at cheaper cost – the DR yoke also has back-swept clamps, but the clamps are not rubber-mounted like the RM ones. I think the RM yoke & clamp assembly cost me about $100 (although in very good condition), whereas the DR yoke (in about the same condition) cost me $5 – the DR yoke is lighter too. In due course, I plan to change the RM top yoke for the DR top yoke. I had to make an adaptor assembly for the RM yoke to fit the PE speedo bracket and am now making a different adaptor for use with the DR yoke, but the DR adaptor should be less work than the RM adaptor.

The steering bearings are modern tapered-roller type, but the upper bearing required a small amount of machining to the steering column to fit correctly. The RM bottom yoke I am now using (which came with the RM top yoke as a full set) is a slightly updated version of the PE yoke and uses a pressed-in steering column (the PE set-up uses a looser fit with pinch bolt), but I was luckily able to press the column out fairly easily after heating the yoke...and then reinstall it after machining.
I also modified the RM bottom yoke by fitting additional stops to reduce the steering arc.

One of the steering stops I made:


Each new stop is located by one needle roller and one countersunk screw:


The steering column with its locating circlip removed for machining to suit the top tapered roller bearing:


The top yoke fitted with the speedo bracket adapter I made:


The speedo bracket fitted to the adapter:


The speedo (and hence the front number plate) ends up in the same position as it would be with the standard PE top yoke.


This is the new brake pedal bracket I made, incorporating an anchor point for the rear brake torque arm (slightly bent, standard RM/PE part is on the left):


I copied the design of the brake pedal mount from the photo in this article (kindly supplied by Leith Codrington):


Luckily the standard DR500 torque arm was about the right length for use with this design.


Still more photos and details to follow.


Regards,
James


Last edited by James P on Tue Dec 24, 2019 9:15 am; edited 1 time in total
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James P



Joined: 31 Mar 2013
Posts: 156
Location: Sydney, Australia

PostPosted: Tue Dec 24, 2019 8:19 am    Post subject: Reply with quote

I still have a few more small modifications to do before the bike will be finished (including a shorter side-stand), but it shouldn’t look much different to its appearance in the photos. Just ignore the fact that there is no fuel line fitted in the photos – I forgot to fit it before taking the photos of the bike in the first post. Thankfully I remembered to fit it before turning the fuel on to start the engine!

Here are some photos of the modifications to the exhaust:








Try to ignore the dodgy welding - my TIG skills are 'basic'.


Here is the new stinger/tailpipe with SP Tadao silencer:


I couldn't seem to buy any silencer 'bands' of the correct length, so I made some from aluminium strip. They are lined with thin rubber strip on the inside.

Once I had got the new stinger/tailpipe in the correct position, I blocked the original stinger at the end of the reverse cone by cutting the tailpipe and inserting a plug/sleeve (as seen here before welding):



While in 'welding mode', I thought I should fit a proper spring retainer to the header pipe (the pipe originally came with a large flat washer welded on for this purpose):


Again, my welding could be better, but it seems structurally sound!


There are a few more (possibly) interesting details to explain - see next instalment.


regards,
James


Last edited by James P on Tue Dec 24, 2019 9:17 am; edited 1 time in total
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James P



Joined: 31 Mar 2013
Posts: 156
Location: Sydney, Australia

PostPosted: Tue Dec 24, 2019 8:54 am    Post subject: Reply with quote

Some other details of the bike which may be of interest:

It came fitted with a VM34 carb from a Yamaha TD2 (instead of the standard VM36). I had a TM32 from a mid-model TS250X lying about, which has now been modified internally for better air flow (the �jet blocks� originally formed an oval bore, but these have now been bored out to make a true 32mm carb). I have changed jets where necessary, so it now uses common types rather than the scarce OEM types.
The inlet manifold was custom-made from a block of aluminium to suit a Mk2 Amal rubber sleeve, which happens to fit the TM32 carb. A large K&N air filter is fitted to a custom-made connector elbow, which offers support to the carburettor in the absence of the standard air box (which came with the bike, but was badly cracked).

The carb and air filter arrangement:


The fabricated aluminium 'elbow' rests on one of the frame tubes to support the carb and minimise wear on the rubber mounting sleeve.

The carb and custom-made manifold:


The carb in bits after wet-bead-blasting and burnishing:



The original ignition coil which came with the bike was in reasonable condition and worked, but the insulation on the HT lead was breaking up. Luckily I managed to replace it by drilling holes in the body of the coil unit to unsolder the connection, solder in a new lead and then fill the holes with Araldite.

Photos, part-way through the process and the end result:





The PE250B came as standard without a chain guard, but with a spring-loaded roller chain tensioner. As the original tensioner assembly was missing when I bought the bike (it did have a generic item fitted), I fabricated a new roller tensioner incorporating a mounting for a chain guard (this was made in 2006 when I couldn't weld at all, so I had it welded by a professional...!):



As standard, there is a rather large gap between the ratios of first and second gear. Luckily, fitting the countershaft and first driven gear from the contemporary RM250 models closes this gap. The gap may now be a little closer than I would have wished for, but I think on balance it is better than the large gap which previously existed.
I originally selected the largest front and smallest rear sprockets which were available as factory options (15-tooth and 50-tooth respectively). I bought the chain and both sprockets from The Chain Gang in 2005, the rear sprocket being of the firm�s own make (well made but heavy in steel!). The gearing seemed OK on the road, but I thought I could go a little higher. As I needed a new rear sprocket anyway to suit the DR500 hub I intended to fit, I took the opportunity to specify a 47-tooth sprocket. There are not a lot of options available for the DR500 fitting, so I had a hard-anodised aluminium sprocket custom-made by XAM in Japan � excellent quality at a reasonable price. I had to shorten the chain for the new set-up and am still presently using the clip-type connector link. As soon as I am satisfied with the gearing, I will replace it with a rivet-type link.


Unfortunately, the previous owner had cut off the mounting for the rear brake light switch. I ground off the remainder of the mounting bracket and intended to make a new one and have it welded on. Due to oversight, I neglected to do that last bit before powder-coating the frame when I first rebuilt the bike...Doh! Instead, I fabricated a neat and unobtrusive bracket for this purpose, which attaches to one of the engine mountings and puts the brake light switch in the correct place.

The original lighting system used two separate 6V coils on the stator; one for the headlight and one for everything else. I found a firm in Adelaide which offered a 12V conversion by rewinding the stator coils and connecting them in series for an output of 60W at 12V AC to run the whole system. A voltage regulator has been connected in the circuit, and is attached to a custom-made bracket, which is bolted to the existing mountings for the HT ignition coil, underneath the fuel tank.

Unfortunately, the original handlebar light switches (which came in the box of bits with the bike) were beyond repair. Replacements cost a small fortune...if you can find them. I thus decided to use a Lambretta ignition switch, which has multiple positions for controlling lights etc. The only switches on the handlebar are a simple push-button for the electric horn (also a Lambretta item) and an ignition kill switch. A small toggle switch for headlight high and low beam selection is now fitted to one of the headlight support brackets. I made the wiring loom myself, on account of the use of different switches etc.


Something I always wanted for the PE was a magnetic oil drain plug. These are commercially available, but I thought the quality questionable (heating the body of the plug made the magnet come out - I didn't want that happening in use!). I therefore made my own, using a genuine Suzuki drain plug (still available new). I drilled and tapped the end of the plug and Loctited in a 3mm stud. I bought some circular magnets with 3mm holes in the centre and fitted several of them over the stud. I cut a short length of aluminium tube to cover the magnets and made a thick flat washer to cover the top end, then Loctited a nut on the end of the stud. If a magnet does break, it will not be taken away with the oil and get stuck to/in moving parts. The magnetic field strength is slightly weaker with the magnets encased in this way, but it should still be strong enough to attract and retain any loose steel particles in the oil.

Here is my magnetic drain plug, test fitted in a spare engine casing to ensure it won't foul on anything:



If anyone would like to know anything else about the bike, please ask!


Regards,
James


Last edited by James P on Sun Nov 29, 2020 10:46 am; edited 1 time in total
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Howie



Joined: 18 Oct 2009
Posts: 511
Location: Kwaksville

PostPosted: Tue Dec 24, 2019 4:03 pm    Post subject: Reply with quote

That is just fantastic James Thumbs Up

Hopefully that fat bastard, Santa will bring me some of your engineering skills?

Mind you I haven't been particularly good this year Dance
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mikog
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Joined: 10 Jul 2008
Posts: 5
Location: West Yorkshire

PostPosted: Tue Dec 24, 2019 8:27 pm    Post subject: Reply with quote

I`ve been working on 2 strokes for decades now and have never seen that done to the stinger before, it does make perfect sense when you think about it. It opens up more easier options of putting bigger two stroke engines into Gag Bikes.
I take my hat off to you, you`ve done a brilliant job.
Thank you for such a detailed and informative post.
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James P



Joined: 31 Mar 2013
Posts: 156
Location: Sydney, Australia

PostPosted: Tue Jan 14, 2020 9:22 am    Post subject: Reply with quote

Thanks Howie & mikog. I'll add some more info if/when there are any developments.

Regards,
James
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