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Post by victor on Dec 17, 2017 22:36:01 GMT 1
My rebuilt RD350 ypvs F2 ran when I first put it together but then suffered some electrical gremlins (intermittent spark) which seemed to be solved by a new rectifier after a new coil did not improve things (I do not understand why but it now has a reliable spark).
I went out on it 2 or 3 times and it was OK but then I took off the carbs as they were leaking. On replacing them it struggled to start though I eventually got it to run on one cylinder. So I swapped the carbs over but could not get it to run. swapped them back and can not get to start. I have since stripped the carbs again to make sure no blocked jets and have transparent side tubes to show there is fuel in them but no sign of it starting.
I have checked for any sign of water in the exhaust ports, checked the operation of the power valves and repeated the leak test (does not hold indefinitely but does seem to keep a few psi for a few minutes). The spark is consistent. not the strongest I have seen but it has not obviously changed from when it was running.
So I have essentially run out of ideas and just want to give the thing a good thrashing!
Any help appreciated as incredibly frustrating having got to the end of the project and it just does not run.
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Post by Yogi on Dec 17, 2017 23:22:03 GMT 1
1. Is the balance pipe on the inside between the carbs
2. Is the vacuum pipe connected from the pet tap to the inside of the right carb
3 Are the float bowls on the correct carbs
,the bowl with the small hole in the bottom should be on the choke side carb(left)
4. Have you set the float levels in both carbs
5. If all else fails send them to Muttsnutts
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Post by jakethepeg007 on Dec 17, 2017 23:47:51 GMT 1
Have you tried new spark plugs, if the spark isn’t great they might be breaking down under combustion pressure
Cheers
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Post by cb250g5 on Dec 18, 2017 11:41:36 GMT 1
Assuming you have the standard Yamaha ignition system, the rectifier is not part of the ignition system, so that's a red herring.
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Post by victor on Dec 18, 2017 13:50:05 GMT 1
Yogi / Jake / CB
1.Balance pipe is on (though could not use when I swapped the carbs over)
2.Using a remote fuel feed so vacuum should not be needed
3. Need to check float bowls - think I did but will recheck. When you say hole, one has a short pipe sticking up and one just a hole just inside of the bowl edge - is that what you mean and it should be the one with just a hole on the choke side?
4. float heights both set
5. Fitted new iridium plugs
6. I had the same thinking on the rectifier but I think the old one was leaking to earth so may just have been affecting the battery.
Greg
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Post by cb250g5 on Dec 18, 2017 14:39:49 GMT 1
Yogi / Jake / CB 6. I had the same thinking on the rectifier but I think the old one was leaking to earth so may just have been affecting the battery. Greg The Yamaha ignition system does not use or need the battery for sparks. There are separate generator coils feeding an AC voltage to the CDI. Take a look here, for a simplified diagram rdlccrazy.proboards.com/thread/6062/spark-on-ypvs-help-lads |
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Post by Yogi on Dec 18, 2017 14:45:29 GMT 1
If your using a remote tank you need to block the vac pipe on the right carb
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Post by victor on Dec 18, 2017 19:00:56 GMT 1
Thanks Yogi
I have progressed a bit, I had stupidly put the balance pipe in the wrong place, it now starts again but only running cleanly on the LH side. I will try blocking the vac pipe.
Greg
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Post by victor on Dec 19, 2017 18:31:37 GMT 1
Blocked the vac pipe and now seems to be running OK.
Thanks for the help, I had just assumed as the vacuum was not needed to provide fuel I could forget about it ........ good to learn from mistakes and hopefully not repeat!
Greg
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Post by Yogi on Dec 19, 2017 19:21:35 GMT 1
Glad to hear she's running again Greg
Carbs can be a nightmare
Atb Matt
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Post by cooper on Dec 20, 2017 15:13:44 GMT 1
when my bike only ran on one cylinder.it turned out to be the cdi unit
put a used one on and all was ok again
strange as it was working fine before i stripped the bike .
glad you got it all sorted thou....
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Post by victor on Apr 9, 2018 22:10:37 GMT 1
Although I thought all my problems were solved ....not the case!
Having not run the bike for the last couple of months because of the weather when I came back to it would not start again, however if I drain the carbs and then reprime them it starts and runs well. After a trip out and then allowing to stand for an hour it would again not start until I had drained the carbs again.
It is as if the carbs are flooding but nothing is coming out the carb overflows until I open them. Also when the overflow was open the fuel continued to flow which I was not sure was correct for a vacuum tap?
The float heights are set to standard with new float jet/needles and the fuel level looks OK (clear side tubes) so I am confused as to what is happening. Has anyone got any ideas?
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