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Old 10-06-2014, 04:53 PM   #1
jm76 OP
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Joined: Jan 2013
Oddometer: 15
R90/6 won't idle but otherwise appears to run fine.

My R90/6 suddenly won't idle.

When I start it up cold or hot it just dies unless I give it throttle and I can keep it running at ~750 rpm with just throttle. Nothing was adjusted on either carb. It had a rough cold idle but idled fine after warming up. This happened suddenly, as in it was idling fine and then at the next stop light died and now dies every time without idle.

I'm not finding vacuum leaks and replaced the spark plugs with proper gap just to be safe (I've had the bike for a little over a month and figured it was a good idea to check them anyways).

Would a clog in one carb cause the bike to not idle or am I looking for something else?

On these carbs can you back the idle screw out completely and spray carb cleaner in to see if there is something to dislodge?

Any other ideas before completely stripping them down and rebuilding?

Thanks,
Jim
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Old 10-06-2014, 04:57 PM   #2
CafeDude
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Have you checked to see if both idle jets are clear and not plugged up?
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Old 10-06-2014, 05:07 PM   #3
chollo9
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Hey Jim,

Check the float bowls for water and/or dirt first, just to get an idea of what might be upstream, although water would usually cause rough running above idle too. I'm guessing some trash got in your low speed circuit. Once the bowls are off, I'd squirt some carb or contact cleaner through the low speed jet on each side, then do the same through the passages beneath the fuel mixture screws (turn them in while counting the turns until they seat lightly, then take them out, with the spring that comes along--do your squirt/clean, then run them back in all the way, lightly, then back out the original amount).

This may take care of the problem. Or not. But it's what I would try first.

Well, I guess first you could look and see if the idle adjustment screw(s) fell out, but I doubt that.

Posted while he ^^ was posting, we're both talking about the same thing.
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Old 10-06-2014, 05:07 PM   #4
Dirt_Boy
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Hi Jim, disconnect the battery eg the red/ hot lead, pull the the plugs, remove the three Allen key bolts and remover the front cover.

Grab a six mill Allen key, insert it into the allen head bilt in the crank a turn the motor by hand clock wise. Check to see if the points are opening on the highest part of the cam. The bump part.

Losen the screws that locate the points and open them up to 15 thousands of an inch. Use a bent feeler guage to check the gap.

Dab a little bit of grease on the cam lobe while you are there. Re check and adjust your timing. Refit the front cover, make sure the points wire doesn't get trapped under the cover. Cheers
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Old 10-06-2014, 05:08 PM   #5
Beemeup
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Mine recently started running like crap and the idle jets were sludged up. Pristine not long ago. I got some bad gas somewhere.
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Old 10-06-2014, 05:08 PM   #6
Fletchlivz
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Well one nice thing about the Bing carbs is how easy they are to get at without having to 'rebuild' them. Pop that bowl off and check the jets for blockages. All it takes is a tiny piece of crud. I'd start there (skipping other super obvious things like fuel being below the reserve level, etc...)
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Old 10-06-2014, 05:22 PM   #7
disston
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Do a complete tune up.

1...Adjust the valves.
2...Check and adjust the points, timing.
3...Balance the carbs.

Details are in any manual, you should have either the Clymer's or the Hayne's manual.

It may be a little surprising but a condition of no idle may be caused by any of the three adjustments mentioned above.
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Old 10-07-2014, 04:30 AM   #8
chasbmw
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If you adjust the mixture screw and nothing happens, then it is an indication that the mixture circuit is blocked.

Fit proper fuel line, that is proof against ethanol or you will find that your fuel line will shed little bits of black rubber than get everywhere.

If you don't use your bike over the winter period, remove the float bowls to drain down the carbs.
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Old 10-07-2014, 08:00 AM   #9
silverhead
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While it's running, spray carb cleaner around the air mixture screws to make sure it doesn't change the speed the bike runs at. If it does, replace the o-rings on the air mix screws.

But otherwise, if it just started doing it, I'd use the red straw on a can of carb cleaner to spray into the pilot jet hole while holding the throttle open so the two tiny holes under the butterfly might have a chance to clean themselves out. I just completely tore down/cleaned my carbs on my R90/6 last week and the right side carb's pilot circuit was completely blocked. I had to use guitar string to bust through the plugged up holes under the butterfly as well as clean out my pilot jet.

Now my bike idles correctly and fires right off when I hit the starter button, even if it's cold. I rode it in 45F weather this past weekend and it fired up on choke no problem.
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Old 10-07-2014, 10:45 AM   #10
Horsehockey
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Quote:
Originally Posted by disston View Post
Do a complete tune up.

1...Adjust the valves.
2...Check and adjust the points, timing.
3...Balance the carbs.

Details are in any manual, you should have either the Clymer's or the Hayne's manual.

It may be a little surprising but a condition of no idle may be caused by any of the three adjustments mentioned above.
What Disston said. Start with the valves.
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Old 10-08-2014, 04:33 AM   #11
squizzy
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Many years ago, my R90S would not idle whilst I was on a club run. OK with acceleration, but would die when stopped. Bit more rattly than normal. Rode home and removed the rocker covers and a bunch of needle rollers fell out on one side. New rollers fitted and good as new. Sold the bike several years later , and was still running fine.
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