Running Weird

[bob393]

This sounds like a problem we have all had.
This is my story on my 1994 750.

Choke on starts perfectly!
Turn choke off it dies. Restarts fine with choke but has a dead throttle.
I know it's cold!
When it warms up choke off runs OK. When it's hot bottom end is great up to about 2000 rpm's. Dead up to about 5000 than it's fine.
In general it smells like it's running rich but the plugs are light tan and new under 500 miles.
Also it seems the #3 cylinder lags behind the rest, well perhaps not #3 but one of the seems to lag a bit.
I'll tell you when it catches at about 5000 rpm's you have to work to keep the front wheel down. It hits hard!

Strange huh?

[Kreylyn]

Check the valves, clean the carbs, sync the carbs... inspect all rubber as you go and replace any dry/hard/cracked pieces everywhere.

Krey

[bob393]

Sounds like you mean start at the beginning!
Check the valves your talking the adjustment right?

[Kreylyn]

Sounds like you mean start at the beginning!
Check the valves your talking the adjustment right?

Yes, adjust them if needed. This is the first thing I would check.

Then I would clean the carbs, do a full inspection on them. all orings, jets are clean, emulsion tubes are in good shape.

Then with clean carbs put them back on and sync to the newly adjusted valves.

If you have not done those things recently, it's best to "start at the beginning" as you put it, yes. If you have.. .then say so and lets move to more detailed trouble shooting.

But yes... the first step is always basic maintenance items... tune, clean, adjust.... then if you have running problems, we can go from there.

Krey

[bob393]

I did pull the carbs off and give them a quick cleaning. Just spray gumout and air. They were filthy! I'll dig in a bit deeper and see what I find. It seams that the carbs are problematic on these bikes. Would you agree?

[Kreylyn]

I did pull the carbs off and give them a quick cleaning. Just spray gumout and air. They were filthy! I'll dig in a bit deeper and see what I find. It seams that the carbs are problematic on these bikes. Would you agree?

If you did not remove, and soak the jets then they are probably not actually clean, especially if the carbs were as dirty as you suggest.

I would recomend getting a can of carb dip ($20 at an auto store) and soak the parts at least 12 hours completely disassembled. Use the spray cans of carb cleaner as a rinse, blow dry with forced air, then inspect. Actually hold the jets up to a light and closely look to see that the holes are open, perfectly round, and light can reflect off the inside of the jets. If not, varnish is still present... soak them more, clean them again.

As for "problematic".... not so much the carbs, as the newer fuel mixtures out there break down faster, varnish up quicker, and or absorbe water faster... causing more issues for an unsealed system (any carbs).

Krey

[bob393]

Thanks, that's good advice! This bike did spend a lot of time just sitting around in it's life. I got it with about 4500 miles on it and it hadn't been registered for the last 8 year!

[bob393]

OK,

The valves are adjusted, the new plugs are gaped, and the garbs are soaking!

I'll let you know the outcome.

[bob393]

Well I found a missing part. There are two nylon washers on top of the needle jet and one is missing. I bet that could have something to do with the sluggish cylinder!

[Kreylyn]

Well I found a missing part. There are two nylon washers on top of the needle jet and one is missing. I bet that could have something to do with the sluggish cylinder!

One is the spacer donut that goes under the eclip, one is the spring seat to push down on the needle on top of the eclip. Which one is missing?

Krey

[bob393]

The spring seat on top.