R90/6 having engine issues

[TexasAirhead]

Finally had some time to go through the bike. Cleaned the right side carb and adjusted valves. The intake valve was tight, so I set everything to .006" intake and .008" exhaust. Checked plugs, wires and coils. I started the bike and pulled the left plug and the bike kept running. Connected both back up and started the bike again. As soon as I pulled the right plug wire, the bike shut off immediately. Left cylinder wouldn't fire. So, I moved on to left side. Pulled the bowl and level was low. Cleaned the carb and adjusted the float level. BAM! the bike runs again. I think the left cylinder wasn't running because it wasn't getting fuel.

I let the bike warm up for a bit. Sounded really good. Soon as I took the bike off the center stand, the idle went up. As I backed out of my garage and went on a slight slope, the idle dropped back down. As I rode off, the bike pulls like a beast. Way better than it did even when I first got it a few months ago. I didn't know what to expect from a 40 year old bike when I bought it and thought it was just sluggish from old age. I was pleasantly surprised! Throttle was way more responsive. But when coming to a stop sign, the idle just shot up and stayed up around 2,500 rpm and wouldn't come down. What could be causing this? Running too rich? Adjust idle? I never adjusted any of the jets when cleaning the carbs. The only thing I removed was the float needle. I've never tuned carbs before, but so far this bike is easy to work on.*knock on wood* Are there baseline settings ( I guess I should look that up) to set the carbs at? Or what could be causing the super high idle? Adjust idle screws first or start messing with jets first? Or do float levels affect that? Maybe I allowed for too much fuel in the bowl or something.

Ahh yes, the learning curve

Thanks again for everyone's help and advice!

[TexasAirhead]

I think for now I'm going to check for any vacuum leaks before or after the left carb. Double check the throttle cables and slack. Do a proper warm up and ride for a little while. Adjust idle screws after warm up, one cylinder at a time. Then get baseline settings for jets. Zero everything out and sync carbs. I'm hoping for now that it's not something dealing with the advance or electrical and just carb tuning issues.

When stopped at a stop sign and the clutch is pulled in, the bike maintains high idle rather than dropping down. Once in gear and slowly taking off, the idle drops down as the gearing is applied. But when slowing down the idle wont go back to a resting point.

[Deleted User 62]

Sounds like a sticking advance unit to me. Have you ever removed and cleaned/lubed it? Do you have a strobe timing light?

[DucatiPete]

Ahh, troubleshooting...

Double check the throttle cables and slack.

That's where i'd start, given what you've said.

It sounds like you're on the right track - ie you've got to get back to a baseline and original settings then *slowly* work up from there...

Good luck! I know how frustrating issues like you're confronting can be, but you can probably rest assured that it's not a major problem.

[TexasAirhead]

I do have a timing light that I borrowed from my brother in law. Never used one before aside from yesterday just to peek into the viewing hole. Have no clue how to read it though. I assume you want to see the S inside the window, but not sure if it's supposed to line up like the OT or just bounce around in the window. One S showing or two S's showing or whatnot.

Sorry for the noobie questions. I appreciate the info along with knowing I have quite a bit of reading to do!

[DucatiPete]

From memory: with the timing light you want one S lining up in the middle of the hole at idle, and the F(?) lining up at ~3200rpm.

[SteveD]

Might be tight cables, might be inadequate free play on the cables, might be tight valves, might be the throttle screws if set in too far?

I'd ensure the clamps are all tight. If you grab a carb, is it easy to rotate? it shouldn't be.

Then I'd check the valves. Then I'd set the throttle cable. Get a very thin feeler gauge and run it thru where the throttle cable causes the throttle arm to move. With both sides equally set via the gauge, then rotate the screw cw x 1/2 turn. Take it for a 20 mile ride to warm it up.

Then if it still idles high use a flat screwdriver to move both throttle screws ccw (out) one side then the other. Try a 1/4 turn first, wait a few moments to see if it settles. If not go some more. If it settles too far, go cw a little. To and fro like that 'til you're happy.

[Deleted User 62]

Yes, the S mark should be centered in the hole at idle. It may bounce around a bit, or you might see two images. That's a different problem. The F mark should be centered in the window at full advance, around 3000 rpm. Something to try, when it's idling too fast; turn it off and then quickly turn it back on before it dies. Does the idle drop? If so, the advance is most likely sticking.

[Duane Ausherman]

Sounds like a sticking advance unit to me. Have you ever removed and cleaned/lubed it? Do you have a strobe timing light?

There is a 5 second test for a hung up advance mechanism. Start there . Use Google on my site.

[ME 109]

Sounds like a sticking advance unit to me. Have you ever removed and cleaned/lubed it? Do you have a strobe timing light?

There is a 5 second test for a hung up advance mechanism. Start there . Use Google on my site.

Got a linky there Duane?
Texas airhead may not know you from a..........well, just don't let him go to Diane's site.