Diff'rent Strokers

arlurt · Posted: Tue Dec 22, 2009 4:43 pm Post subject:

Hi Warwick,

Thanks for all you input, interesting stuff.

Yamaha must have considered there to be a significant advantage in the power jets or why would they go to so much trouble to have them on the SP for homologation?

As a start point I'm going to run the standard SP carbs, without power jets, and with the restrictors fitted. Once I've got a stable baseline I might start to play about a bit... Cool

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Wb · Joined: 22 Jan 2007 Posts: 49

Sounds like a sound plan.

Of course the electronic powerjets (along with all the other SP bells and whistles) certainly do offer some potential performance advantages - but, in the case of the electronic bit of the PJs, probably not until you are fighting for the lead in an early nineties Jap proddy race round Sugo Laughing

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That's not to say an SP is not a great bike of course, but, to be honest, in 45Bhp mode, I'd take an R or RS over an SP anyday really. The R /RS were actively built to make 45 ponies, and so do so very well indeed, whereas a stock SP always feels a bit too much like a restricted bike to me, and is thus not quite so satisfying to ride on the road I reckon (much like the SP models of most race reps). Of course the plus side is that the SP is easier to liberate - and has everything already in place for when you do Cool

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arlurt · Posted: Sat Dec 26, 2009 7:27 pm Post subject:

Can anyone tell me what size air jets I need in positions 1,2 and 3 in the solenoid air valves for my 3XV for the 91/92 SP engine with 36mm carbs?

I've seen people selling "SP" air valves, but surely they're the same as the R and RS, just with different sized jets?

Any info gladly received.
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Wb · Joined: 22 Jan 2007 Posts: 49

Yes, same actual units AFAIK. Don't know the jet sizes offhand. I'd imagine they differ between the two units though - like the R & RS ones. An additional variable is whether the R/RS CDi will activate them at the 'right' time as the carburation differs quite a bit betweeen the R/RS and SP of course. Which CDi do you currently have: -00, -40 or -60?

I'm really not at all sure how much of an issue it would be if the variable air jet stuff is out of whack though? And it may very well be work-roundable?

eire_kp61 · Joined: 05 Jul 2008 Posts: 43 Location: Kilkenny Ireland

Coming along nicely now karl Very Happy

If only mine will come togeather as fast haha , Its looking very sick now after standing so long .

Wb · Joined: 22 Jan 2007 Posts: 49

arlurt · Posted: Thu Dec 31, 2009 10:29 am Post subject:

Thanks Wb.

"VAJ" - Variable Air Jet?

I've been away for a few days, visiting relatives. Now I'm back I'm full of cold and feeling pretty misserable. I'll get in the garage soon and finish off the SP carb swap, and have a look to see what jets are in the RS air valves.

At the moment the bike is running the -00 CDI, but I've got a -40 as well.

All the best to you for 2010.
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arlurt · Posted: Thu Jan 07, 2010 1:39 pm Post subject:

My "From Japan" bits came the other day, a little quicker than expected.

Delighted with the signle seat cover, lovely factory paint and decals. It's not as new as the original packaging pretends it is, but I'm still well pleased.

The under seat plastics are spot on. Unmolested, with original reflector and indicators thrown in too. I've shed the pillion foot rests, and had to trim the number plate a bit to fit above the reflector, but I think it will all work OK.

If I'm going to be doing any more "test rides" in this grotty weather, (probably not while there's still snow on the roads!) then the full rear mud-guard really is what's required. Must be turning sensible in my advancing years... No, hang on, I've got a 3XV. Rolling Eyes

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Kneedown · Joined: 18 May 2009 Posts: 5 Location: Perth, Australia

Hey arlurt

Great to hear you have your bike back up and running!

I'm reading your progress (and new direction) with great interest as I've got myself an SP engine & carbs for my 3XV R as well. So far have not fitted the engine as I was planning on rebuilding the top & bottom end before using it as a precaution (unknown history). Now I'm more tempted to jump right in...

I have a 3XV-70 CDI & Sugo chambers as well, so hopefully that will liberate everything the SP engine has to offer when I get it all together.

Good luck and keep us posted! Cool

PS: That seat cowl looks great...what was the going rate for that if you don't mind?

arlurt · Posted: Tue Jan 12, 2010 1:54 pm Post subject:

It’s been three and a half years since the RS engine blew up, so my memory’s rather hazy, but riding the bike with the SP engine and RS carbs, it felt like it had more mid-range pull than the RS set up did.

If the thing had run cleanly on the RS carbs I would have left it like that, but because my half-hearted attempt at clearing the part-throttle and tick-over problem failed, I decided to give the SP carbs a go.

It’s not a simple swap. The 36mm SP carbs are much bigger in all dimensions than the 28mm RS ones. The left carb is right up against the wiring loom, the right looks very close to the radiator. The RS fuel and air pipes either don’t reach, or don’t fall easily in to place for the SP carbs. Fuel inlet, overflow, drain, variable air, pet-cock vacuum, all a pain. Carb heating, that I’m not that bothered about, all lines up fine.

I haven’t looked yet, but I suspect the electronic Variable Air Jets will be different between RS and SP, thanks to Wb for the SP data, I just haven’t checked the RS yet.

The air-boxes are different, the rubbers from air-box to carb are different. I don’t know yet if the RS throttle handle has the travel to open the SP carbs all the way, but maybe that doesn’t matter anyway because of the restrictors in the SP rubbers are smaller than the 36mm chokes.

The SP 1st Gear is significantly taller than the R/RS, which as Wb says probably won’t be an issue when the bike is running better, but was a problem trying to ride it in bad weather with only one cylinder working on part throttle. I think I will fit the RS gearbox to the SP engine. If I manage to get to the TT on it this year, there are several places we go on the island where there are steep tight hairpins, and some ultra-tight back-road-tracks where I don’t think it will cope.

Do let me know how you get on with the engine swap, hopefully we can help each other… Laughing

The Seat cover was on Yahoo Japan. My winning bid was 8050 Japanese Yen, which at JPY145/£ is about £55. By the time you've added Yahoo shipping, From Japan commission, shipping from Japan to the UK, and UK import duty, the cost was about double the price of the item. I'd been looking for one for a while, and have seen them sell for twice what I paid in the auction so was happy at that. I had also considered buying a pillion seat an making a single seat unit but eventually convinced myself that the time and cost of this justified just buying one.
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arlurt · Posted: Fri Apr 23, 2010 6:15 am Post subject:

Well, as usual for me, nothing's happened for months.

I was busy at work at the start of the year, preparing for another India visit, which at least has gone well, but when it was time to come home I was hit by the Volcano trouble. If UK airspace had closed ten minutes later I might have been in the air and en route to Dubai, but as it was all UK passengers were off-loaded and sent back through immigration to cancel exit stamps and collect bags.

Two more attempts to leave the country both failed, I now have a flight out late tomorrow, but it's going to be a long trip home. Four hours to Dubai, a five hour wait and then eight hours to Heathrow. My original ticket was to Manchester and a far easier run home, but at least I will be back in the UK. Just over a month in India is too long.

The plan to go to the TT on the 3XV is still there, but now I've only got a month to get it back together and convince myself it will stand up to the trip. There's been no change to the bike since my last post. I know the engine runs on the RS carbs, maybe I should sort them out for a quick fix and come back to the SP carbs and a proper engine rebuild when I get back...

Looking forward to playing with my toys again. Very Happy

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arlurt · Posted: Mon May 10, 2010 8:51 am Post subject:

I had a ride round the block on the 3XV on Sunday. I thought that I really should get it back together and see if it's a realistic proposition for the TT or not.

It took me about six hours to change over the reedblocks, carb rubbers, modify and fit the carb/airbox rubbers, and plumbing. It's running the 36mm SP carbs, and running cleanly on both cylinders. There are a few minor problems to sort out... First a reluctance to drop back to tick-over, which I think may be a throttle cable problem, just a bit tight. Secondly a fuel leak from one of the overflows which looks like a sticking float.

The carbs are getting full throttle with the RS throttle handle, and everything did seem to go back together without too much difficulty, but I did have to make up new fuel lines, and airlines to the solenoid valves, and carb heating lines to the right cylinder. It's running with the power-jets disconnected.

After much agonising I removed the steel 28mm restrictors from the carb rubbers and removed the rubber retaining lips to open them out to full diameter. I've got bigger-than 38mm openings right through the rubbers now.

I also opened out the inlet to the left cylinder airbox.

The restriction in the inlet to the right airbox appears to be the rubber that runs under the frame rail, rather than in the hard plastic of the airbox. Not really sure what I can do about that.

I'm nervouse that it doesn't seem to be smoking as much as it did before, have to check the oil pump setting. And the battery is shot.

It wasn't enjoyable to ride at all. It bogs down in the over-tall SP first gear, dripped fuel when I stopped, and seems to have developed an oil drip as well, which I can only assume is from the gearbox somewhere. At present I wouldn't go to the chippy in the next village on it, never mind the TT for a week with it as my only transport....

I did fifty miles on the Fireblade as well, just to make sure it was OK, and that's sealed the fate of the 3XV for this years TT. I'll take the 4-stroke.
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wullie mckie · Joined: 20 May 2008 Posts: 16 Location: Fife, Scotland.

Hi Arlurt.
It's been a couple of months or so since I chided you about your lack of progress on your VERY long term engine rebuild.
I'm very happy to see you've made some serious progress at last ! Don't stop now, your nearly there !
Once it's finished & running well, have you any plans to take it to owners club bashes or bike shows etc. ?
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arlurt · Posted: Sat May 15, 2010 8:09 am Post subject:

I was pretty de-moralised having ridden it last week. It seemed to be fighting me every step of the way, anyone would think it didn't want to be ridden. It really souldn't take six hours to swap carbs and reed-blocks on a bike. Her-in-doors is working on Sunday, so I'll see if I can sort out the throttle cables, (nasty-over-complicated-Yamaha-hotch-potch) and at least get the thing running properly so it'll pass an MoT.

It might be as simple as a cable not being properly seated into the plastic compensator/combining box thing under the tank, or maybe it just needs some slack on the adjusters on top of the carbs. I'll have to have a look at the workshop manual and see if I can figure out how to set up the cables and oil pump properly.

I've taken some photos as I've messed about with it so I'll try and post those over the weekend as well.

Having broken my own rules about just putting it together as standard so that it works, I'm still tempted to look at gutting the spare pair of exhausts I've got to see if I can better match the exhaust side to the "improved" (?) carbs and inlet.
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arlurt · Posted: Sat May 15, 2010 5:00 pm Post subject:

It's back together.... But won't start! Rolling Eyes

What did I say about it fighting me all the way?

I think the battery has given up what little go it had. The Optimate says it's charged, but the bike says it's not. I tried HG in town, and they don't have one. I asked for the battery part number, because apparently there wasn't a 92 Yamaha TZR250. I've bought one on eBay, hope to have it next week.
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