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Classic Bike Trackdays

SDR running poor!
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2TV owner



Joined: 22 Mar 2012
Posts: 146
Location: West Yorkshire

PostPosted: Tue Apr 10, 2012 1:07 pm    Post subject: SDR running poor! Reply with quote

First real ride out on my newly purchased SDR and i found that it dosen't seem to be running as it should.
It starts ok and idles lovely. When riding it seems to have a big flat spot mid throttle but if you ride through mid throttle it goes like stink!
It seems to hunt around on part throttle openings. I know the carb has been 'refurbed' to what standard i'm not sure. When i got back i whipped the plug out and i thought it looked very clean (it is a new plug) also it looked a bit damp. Now i'm no 2stroke expert but i would have thought the plug should have had a bit more carbon on and been dry (correct me if i'm wrong).
Before i dive in does anyone have any advice. Also whilst riding on load i thought that it was smoking more than it should, again not 100% sure as ive not had a 2 stroke for more years than i care to remember.

Thanks in advance!!!! Justin
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StrokerBoy
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PostPosted: Tue Apr 10, 2012 1:33 pm    Post subject: Re: SDR running poor! Reply with quote

2TV owner wrote:
It seems to hunt around on part throttle openings.

Sounds familiar ! My SDR (OK, the wife's... Embarassed ) does the same thing. It's standard as far as I know, and though it ticks over fine and runs well at the top too, it's not happy just trundling along in traffic. Think arlurt's modified one does the same, but he'll no doubt be along to contribute shortly.

2TV owner wrote:
Also whilst riding on load i thought that it was smoking more than it should, again not 100% sure as ive not had a 2 stroke for more years than i care to remember.

Check the oil pump setting (should be alignment marks on both 0 and 100% throttle) but too much smoke/oil is better than not enough... Wink
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2TV owner



Joined: 22 Mar 2012
Posts: 146
Location: West Yorkshire

PostPosted: Tue Apr 10, 2012 3:34 pm    Post subject: Reply with quote

Ok thanks for that, any ideas why the plug seems wet tho'. I am hoping to get over to sherburn this Thursday, just didn't want it breaking down if it's something that needs attention. Although it is a 2 stroke so anything could happen!
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Top-shaggy
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PostPosted: Tue Apr 10, 2012 11:48 pm    Post subject: Reply with quote

Smoking heavily or water vapour?
Please forgive me if I'm stating the obvious but have you checked that the head gasket is not leaking ? Bubbles in the expansion tank may give it away, perhaps a slight leaching of water into the crank cases?

Not a SDR expert - just had my fair share of similar issues on my own 2T bikes etc Shocked
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2TV owner



Joined: 22 Mar 2012
Posts: 146
Location: West Yorkshire

PostPosted: Wed Apr 11, 2012 5:49 am    Post subject: Reply with quote

I'm quite sure it's not water as there are no tell tales in the header and it does seem to be petrol on the plug. I'm going to refuel it with fresh petrol today and take it for a longer run as its only done stop starts and left idling since i have had it and maybe it just wants a longer run?

Thanks for the reply.
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2TV owner



Joined: 22 Mar 2012
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Location: West Yorkshire

PostPosted: Thu Apr 26, 2012 12:47 pm    Post subject: Reply with quote

An update of my SDR,

Iam still trying to get to the bottom of the bike not running properly, decided to investigate down the YPvs route. so itook off the side cover and watched what happened. Ignition on and the valve does it's sweep first anti clockwise then back clockwise so that the setting hole lines up, all good! Start up the bike and i noticed the valve immediately goes anticlockwise which i believe is correct but it starts fluttering all the time. If you rev the engine anything above idle the pulley moves anti clock wise back so that the hole line up again which i think is the fully open postiton. this i think is my lack of bottom end power! back to idle and once again the valve will move anti clockwise and start fluttering again.

I dug out the old 350YPVS haynes manual and read through how the power valve works and studied the wiring diagram and compared it to the sdr. All the same, Bonus! Any way the haynes suggests that a fluttering valve can be caused by a non resistive spark plug. Mine has a new NGK BR9es so its not that. I then checked the resistances of the servo motor and wasn't happy with the readings. A quick look on Ebay found one about 10 miles away. I went armed with the multimeter and thankfully the guy at the shop let me test it. I got the same readings so i was now happy (ish) that the servo motor on my bike was good. He did ask me though had i considered a Zeeltronic system, they make replacement cdi and cdi/ypvs contollers mainly for 350 and 250 yams.

I got on the internet and looked up Zeeltronic and sent them an email asking if they had any info on testing the cdi or YPVS ecu's. Meanwhile i got a new battery on and started checking all the wiring and connections, found a poor connection on the coil so duly replaced that. whilst there i took off the coil and did some resistance checks on it, all good. I checked all of the earths on the bike as i wasn't sure if i had a spike in the wiring or if it was an ECU. I got a small insignificant resistance reading on the negative between the battery and the earth point on the rectifier. I took off the rectifier, cleaned it up and the frame and connector and refitted it along with a parallel wire from the battery to the earth point, on to the coil and down to one of the engine bolts. I now had no resistance on the earth, but still it fluttered.

A guy call Borut from Zeeltronic responded to my email and suggested checking the output from the CDI with an oscilloscope and he sent me a picture of what i should expect to see. We have a Pico scope at work that runs on a laptop so i rigged it up and checked the CDI output and got a screen shot and sent it to Zeeltronic. Borut came back and said that the reading i sent him was not what he would have expected to see on a 350ypvs but he wasn't 100% sure about the SDR. So i still don't know if i have a faulty output on the CDI or if the YPVS ecu is not processing the signal that it has been sent by the CDI.

I am now at the plea stage! are ther any SDR owners out there that might want to let me come along with my CDI and YPVS to plug in to your bike to see if i can identify which is faulty. I live between Leeds and Bradford and am willing to come to you and could also bring the oscilloscope. PM me if you can help in any way.

Justin
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StrokerBoy
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PostPosted: Thu Apr 26, 2012 1:06 pm    Post subject: Reply with quote

Justin, both myself and arlurt aren't that far away from you really and I'm sure one or both of us would be up for this, we could maybe do both together. Very Happy If I - and the SDR - survive this weekend (far from assured, based on how the week has gone so far) we'll sort something out.
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2TV owner



Joined: 22 Mar 2012
Posts: 146
Location: West Yorkshire

PostPosted: Thu Apr 26, 2012 1:59 pm    Post subject: Reply with quote

Fantastic! Very Happy this will be a big help just to know what is wrong. I'm not about much next week or the bank holiday weekend but after that hopefully we can sort something.
weather not looking much fun for Cadwell! two of my work coleagues are there next Tuesday, best get the wets on.
The pics of the TZR don't look pretty, any idea what caused that one?

cheers

justin
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2TV owner



Joined: 22 Mar 2012
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Location: West Yorkshire

PostPosted: Tue May 22, 2012 7:20 am    Post subject: Reply with quote

An update on my SDR,

I found a CDI on Ebay, just plugged it in and guess what, still the same Sad so at least i now know it's not the CDi and i now have a spare. Apart from some obscure spike from somewhere on the bike of which i can't find any it looks like the YPVS controller is not processing the signal correctly that is being sent to it from the CDI. I now need to eliminate this unit either way.
Does anyone know if a YPVS controller from another Yam, ie 350 YPVS would work. I understand that the differences are the rev range at which the valve will open but surely if the wiring is the same it should work?

Justin
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arlurt
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PostPosted: Tue May 22, 2012 12:21 pm    Post subject: Reply with quote

Hi Justin,

Your bike doesn't sound any different from mine, or Tim's. I don't think there's aything wrong with mine or his, other than it being an early 80s two-stroke. Which, to be fair, is the reason I bought it...

Mine used to hunt badly on part throttle, between about 40 and 60 mph in top gear. That was improved by dropping the needle just one groove, but it's never going to be a mid-range torque-monster.

When Tim and I had a ride out together our bikes seemed very evenly matched. Though mine has a Martin Johnson one-off exhaust and end can, and has (I'm told) been ported to match.

If we're ever in the same place at the same time we can have a comparison, but I fear you may find that's just the way it is...

Have a look at the thread further down in here about what I've done with mine.
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2TV owner



Joined: 22 Mar 2012
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PostPosted: Tue May 22, 2012 3:25 pm    Post subject: Reply with quote

Hi thanks for the reply, yes ive read your posts re the poor running. What i need to be confirmed is when you start the bike what does the power valve do? without going over what i have said before i think mine is going to fully open when it is anything other than idle. when at idle the power valve is fluttering. i don't think that's correct. i think it should stay closed and stable until around the 6000rpm mark and then start to open up. Mine is totally gutless as the power valve is open all of the time that the throttle is off idle.

Tim was going to have a look at his to see what his did but couldn't get the power valve pulley cover off and then his tzr blew up!

Any help you or Tim can give with this would be helpful, i'm sick of looking at it now especially as the weather is getting better. Mad

Justin
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PostPosted: Tue May 22, 2012 3:38 pm    Post subject: Reply with quote

Yeah, I've not forgotten Justin, I've just not had chance to look at it again (or the TZR for that matter) or invite you over for a look. Not gonna happen this weekend either I'm afraid... Crying or Very sad
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2TV owner



Joined: 22 Mar 2012
Posts: 146
Location: West Yorkshire

PostPosted: Tue May 22, 2012 4:04 pm    Post subject: Reply with quote

this weekends no good for me either, thanks.
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PostPosted: Tue May 22, 2012 8:42 pm    Post subject: Reply with quote

The SDR is against the wall, inside the Honda, my push-bike, the tandem, and a scarecrow. I've got to check over the Honda this weekend, so while it's out of the way I'll get a video clip of what the power valves does. That'll show you which way it rotates under what circumstances.

Might it just be that you cables have been connected the wrong way round...?
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PostPosted: Wed May 23, 2012 7:56 am    Post subject: Reply with quote

Yes i suppose the cables could be on the wrong way round. that does not explain why the motor joggles about at idle but then again i don't suppose that is a big issue as long as it works.

Look forward to seeing what your's does. Very Happy

justin
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