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monkeybikegirl
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Hi Everyone
I hope this is not too vague. My R90s was set up very recently, with Dellortoes rebuild and balanced. Timing set correctly also. The bike was running great, when out on an short ride, the bike was hard to start back up, sounded terrible and would stumble and want to die. It ran better after reving it past 3000 rpm. That is how I made it home again.
Any ideas on what might be happening?
Thanks very much for any input.

schrader7032
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VBMWMO #7032
San Antonio, TX
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Poor idle and rough starting

Poor idle and rough starting is a symptom of closed valve clearances. Easy check...might be time to do it anyway.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

monkeybikegirl
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The problem occurred suddenly

The problem occurred suddenly and the valves had been set within a 100 km.

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
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Then look at the carbs.

Then look at the carbs. Maybe the low speed jets are plugged up. I would also recheck the valves...every time I set my valves, it's on my mind "did I get that lock nut tight last time?" It bugs me for a while...

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

monkeybikegirl
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I also thought a plug in the

I also thought a plug in the carbs somewhere, because the bike was running great and then started to act up suddenly. Thanks for the tips. a valve clearance check is probably a good idea. Now you have me thinking "Did I tighten the locknut enough".
Thanks Kurt

monkeybikegirl
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I checked the valves and they

I checked the valves and they are correct. Took all the jets out of the Dellortoes and made sure they are clean. The problem stayed the same.

monkeybikegirl
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Also checked sparkplug gap

Also checked sparkplug gap and points gap.

schrader7032
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San Antonio, TX
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What about trying a new

What about trying a new condenser? I assume you still have the stock points ignition system.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Twocams
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I would check for vacuum

I would check for vacuum leaks. Clamps tight,no cracks in plastic tubes ( rubber) to carbs. Carb mounting flanges flat and good gaskets at head to carburetor. Are both carbs getting the same amount of gas in the fuel bowl. Are both filters in the shut off valves clean? If used. Both spark plugs are firing with nice blue spark. Plug gap correct and nice clean electrode area....no soot/gas fouled. Thats all I got for now.
Spark,fuel & air at the right place at the right time in right amount....should run.

twocams

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Twocams
69 R69S 03 K1200GT
92 R100RT

monkeybikegirl
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Still on points, yes.

Still on points, yes.

monkeybikegirl
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Thanks for the tips. The

Thanks for the tips. The weird thing is that it was running great and then a quick stop and it was acting up. No change other then stopping the bike and starting it up 10 minutes later. Well till the next weekend.

Twocams
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Are you using a good premium

Are you using a good premium grade gas. If it has ethanol in your gas you may have to much water to run right. When I have to use ethanol gas I use an additive.

twocams

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Twocams
69 R69S 03 K1200GT
92 R100RT

monkeybikegirl
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94 Octane from Chevron is the

94 Octane from Chevron is the best I can get here in BC.

monkeybikegirl
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VBMWMO #9267
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I just replaced the

I just replaced the conderser. It had no effect. It seems that it is only running on one cyclinder or just barely on one side.

Carott
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Ignition or Carburetor Problem?

A simple test to determine if you have a fuel problem or a spark problem is to connect a timing light and look at the light as the bike runs. Switch the pickup between plug wires to check both cylinders. If the light flashes continuously when the motor stumbles it is likely a fuel problem. If the light flashes intermittently or not at all you have an ignition issue and comparing the two sides can further help the diagnosis. The timing light gives a nice bright light to check for spark and provides information while the engine is running.

Good Luck

Brett

khittner
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Not to throw parts at it, but

Not to throw parts at it, but if your spark plug leads/caps are older, they lose resistance and cause rough running. Not sure that it explains your symptoms' sudden onset, but I'd check them. Snowbum's treatises will have the correct resistance spec for that vintage; I'm pretty sure that the 5K ohms resistance that's necessary for my post-'81 electronic ignition bike is too high for the /6 bikes.

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monkeybikegirl
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I will try that, thanks.

I will try that, thanks.

monkeybikegirl
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VBMWMO #9267
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I believe the wires and caps

I believe the wires and caps are new. It wont hurt to check though. This bike was sitting for over 30 years and only has about 3000 miles on it. the major overhaul was done by a mechanic I trust, but he lives an expensive ferry ride away. I also need to learn to do this myself. I am encouraged by my success with an old r69, but the r90s seems more complicated so far.

monkeybikegirl
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Getting closer to the

Getting closer to the problem. I checked spark from the plugs and one was not sparking as much. New plug which seems to have failed. Bike started much better and ran better after replacing the plugs with the older ones I still had around the shop.. I was able to take it for a ride and it runs great, except when starting out it bogs a bit and needs to be reved higher to get going. It does not do this all the time either. I will test the spark further this week.

monkeybikegirl
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Back to the drawing board.

Back to the drawing board. Weak spark and rough running again. At least I know now which direction I have go in.

schrader7032
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Have you gone through the

Have you gone through the process of swapping electrical components? You've tried new plugs. How about swapping plug wires side to side. You can also put the coil-end of the spark plug wires into the different coil towers to simulate physical swapping of coils. Consider that process of making one type of change and note if the problem you experience switches from one side to the other.

I don't remember if you did this test...Konrad mentioned the ohms of the spark plug cap. Can you take a digital multimeter and put a test lead into each spark plug cap? That way, you're reading the resistance from one plug to the other. Let us know what the reading is. Also, what type of plug are you using? Again, not sure if you've stated that.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

monkeybikegirl
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Good advise, I will do that

Good advise, I will do that this weekend.
Thanks

monkeybikegirl
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VBMWMO #9267
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Looks like with the help of

Looks like with the help of everybody I was able to solve the problem. After checking for spark a couple of times again, the spark seemed inconsistent. I removed the plug wires and replaced them with old ones I had around the shop. Bike runs great. Took it out for 2 hours yesterday and had no problems at all. The spark still only looks yellow not blue. I will order new plug wires as the replacement ones are of unknown origin. The unintended result of this little journey has been that I got to know the bike a little better.
Thanks everyone for your help! I reread the responses many times to make sure I would try everything.

ksiemon
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wires vendor

This is the place for wires...............http://www.motoelekt.com/ignition.htm

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