82 RD350LC not running above 4500, need help

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AZRD350LCGUY
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Joined: Sun Feb 21, 2016 6:53 pm
Location: Gilbert, az

82 RD350LC not running above 4500, need help

#1 Post by AZRD350LCGUY » Sun Mar 27, 2016 5:49 pm

I have a 1982 RD350LC that started to run bad above 4500 rpms. I have checked the low and high speed coils and they are within spec. I have cleaned and rebuilt the carbs several times. New plugs. Good injection oil and only high test gas. New petcock and fuel lines. Checked the float height several times and it's within specs.
When I sit on the side of the road for several minutes with the engine off it will start and run as it should reving in gear to redline without a problem. After about 1 mile it will bog as if it's running out of gas and slowly slow down to about 4000 rpms and will run that was for about a quarter of a mile at 3500 rpms and then will act normal again for about a mile. And them it srarts all over again. It will run all day at 4000 rpms in 6th gear without a problem. Any suggestions??
1982 RD350J aka RD350LC Canadian
1971 Kawasaki F5a Big Horn
2013 NC700X

Judge people by what they do and not what they say they will do.

Moxon
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Joined: Mon Mar 14, 2016 5:18 pm

Re: 82 RD350LC not running above 4500, need help

#2 Post by Moxon » Mon Mar 28, 2016 11:26 am

Sounds like fuel starvation to be honest. Next time it happens, flip it to reserve see if that helps. If not pull the choke out and see if there is any difference. Also when it happens do you get the same volume of exhaust from each pipe? If not you may have one cylinder not firing consistantly. At least then you'll have narrowed down the problem. Good luck.

tacky1
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Re: 82 RD350LC not running above 4500, need help

#3 Post by tacky1 » Mon Mar 28, 2016 3:03 pm

Is the fuel cap vacuum blocked, It sounds like fuel starvation. Run the bike with the fuel cap loose and see if it solves the problem
1985 RZv500
1984 RZ500 Hybrid
1986 RG500 Walter Wolf
1986 RG500 Skoal Bandit
1984 RZ350
1984 RZ350 Hybrid
1981 RD350LC
1981 RD350LC Hybrid
2009 CR500AF Supermoto 250X
2007 CR500AF 250X
1988 YSR50 (2)
1984 GPZ750 Turbo
1989 VFR750R RC30

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2smoke
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Re: 82 RD350LC not running above 4500, need help

#4 Post by 2smoke » Tue Mar 29, 2016 11:45 am

Did you add fuel fuel filters to the bike at some point? They can cause restrictions to flow.
I would also look at the coil wires and caps for corrosion. Did you do the stator tests when the bike was warm?
Colin
79 RD400F Daytona Special
81 RD350LC
89 TDR250
75 Kawasaki H1 500
77 Can-am Tnt250

Moxon
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Re: 82 RD350LC not running above 4500, need help

#5 Post by Moxon » Wed Mar 30, 2016 9:48 pm

If you figure it out, let us know. Someone might have a similar problem and it adds value to the forum to have solutions posted for problems people encounter.

Bare
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Re: 82 RD350LC not running above 4500, need help

#6 Post by Bare » Thu Mar 31, 2016 12:23 am

The Fuel filter tubes in the Stock Petcock can turn to Crap.
Certainly after a 'few' decades.
Pop the Petcock and take a good hard look at it.

AZRD350LCGUY
Posts: 58
Joined: Sun Feb 21, 2016 6:53 pm
Location: Gilbert, az

Re: 82 RD350LC not running above 4500, need help

#7 Post by AZRD350LCGUY » Thu Mar 31, 2016 9:08 pm

Thanks for the suggestions. The fuel petcock is new. It happened with the old petcock as well. I changed out the coil to after market, same result. No fuel filters in line.
I also feel it's a fuel problem.
Does anyone know where to get a more flowing petcock that is a bolt on??
1982 RD350J aka RD350LC Canadian
1971 Kawasaki F5a Big Horn
2013 NC700X

Judge people by what they do and not what they say they will do.

AZRD350LCGUY
Posts: 58
Joined: Sun Feb 21, 2016 6:53 pm
Location: Gilbert, az

Re: 82 RD350LC not running above 4500, need help

#8 Post by AZRD350LCGUY » Thu Apr 14, 2016 4:37 pm

The story so far... I pulled the old (new) petcock and took it apart. Looking inside the I found the passage blocked by about 30% by shrue. After cleaning all that out I put it aside and drained the fuel tank by attaching two long fuel lines and draining into two one gallon cans. The left side drained with full flow. The right didn't drain at all. After pinching off the left side the right started to drain and the left quit. There are two holes coming off the petcock, shouldn't they drain the same?? I looked in my box of RD350LC parts and found the original petcock of the destroyed tank (don't ask) put a O-ring kit in it and installed it on the tank. I put some gas in the tank and took it for a ride. No more problems.
The petcock were sourced from a reliable source but were aftermarket. A lesson to learn here. Always check, take it apart and make sure it the same. It would saved my a lot of frustration and time.
Thanks for all your help.
1982 RD350J aka RD350LC Canadian
1971 Kawasaki F5a Big Horn
2013 NC700X

Judge people by what they do and not what they say they will do.

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2smoke
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Re: 82 RD350LC not running above 4500, need help

#9 Post by 2smoke » Sat Apr 16, 2016 12:55 pm

Glad you are sorted. What was the aftermarket brand? It could save alot of others alot of grief if you name them. I just bought 2 aftermarket petcocks BTW.
Colin
79 RD400F Daytona Special
81 RD350LC
89 TDR250
75 Kawasaki H1 500
77 Can-am Tnt250

AZRD350LCGUY
Posts: 58
Joined: Sun Feb 21, 2016 6:53 pm
Location: Gilbert, az

Re: 82 RD350LC not running above 4500, need help

#10 Post by AZRD350LCGUY » Fri Apr 22, 2016 6:52 pm

I normally buy from yambit.co.uk, but I got these off ebay. Sorry don't know who, it was several months ago.
1982 RD350J aka RD350LC Canadian
1971 Kawasaki F5a Big Horn
2013 NC700X

Judge people by what they do and not what they say they will do.

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