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Discussion Starter #1 (Edited)
Hi people.
I'm in desperate need of help. I'm working on this bike for a friend. Bike last ran in june 2018. Out of the blue it wouldn't run anymore. In oktober I got started on it. I suspected the carbs so first I took them off and took them apart. Cleaned all the parts in an ultrasonic bath. Put everything back together. It wouldn't run. So I started to check all the ignition components. Turned out the camshaft sensor on the rear cilinder was faulty. I got a second hand one. The bike started but ran on front cilinder only. Rear cilinder didn't work en sparkplug came out soaking wet. So back to the carbs. Took them apart again. Checked float level, vacuum membrane, the works...all ok. Bike still runs on front only. Did compression test; front 10 bar, rear 11 bar. Did a measurement of all the ignition components again and all are within the workshop manual specifications. Only thing I can't check are both CDI's. Replaced both; bike still runs on front cilinder only.
Now I'm on the end of my knowledge.
Does anyone has an iedear??
I'm lost.

Hans



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Did you actually see there is spark or not on the rear cylinder?
If not test the pulse generators on the right end of the crank to see if one is bad.

They usually measure about 450 ohms. And some have failed when hot.
 

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Discussion Starter #3
Did you actually see there is spark or not on the rear cylinder?
If not test the pulse generators on the right end of the crank to see if one is bad.

They usually measure about 450 ohms. And some have failed when hot.
If I cranck the engine with the plug outside on the block, I actually see a spark. And like I said; I checked all ignition components according workshop manual specs and all are within given specs, including pulse generators. The bike isn't running long enough to get hot. It runs on one cilinder from the start.

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If you have the air intake tube off get it running and spray a little carb cleaner into the dead cylinder carb to see if it picks up for a little bit.
Are the carbs synced? Both throttles need to work equally.
 

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Discussion Starter #5
If you have the air intake tube off get it running and spray a little carb cleaner into the dead cylinder carb to see if it picks up for a little bit.
Are the carbs synced? Both throttles need to work equally.
After running for 20 seconds on front cilinder and a few backfires from rear cilinder, the sparkplugs from rear are soaking wet. So there is fuel.

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I remember a fellow had a bad running problem from one carb and took it back apart and found he had dropped out the small brass piece that sits in the throat below the needle. It would actually be the main jet outlet ,and the needle controls fuel rate when it drops down into it. See if that is missing on the trouble carb.
 

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Discussion Starter #7
I remember a fellow had a bad running problem from one carb and took it back apart and found he had dropped out the small brass piece that sits in the throat below the needle. It would actually be the main jet outlet ,and the needle controls fuel rate when it drops down into it. See if that is missing on the trouble carb.
You mean this part? If you enlarge the picture of the bowl, you can see it's there


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NO, look into the throat and see if there is a brass piece at the bottom where the needle slides into. I am not sure they all have a removable piece in there.
 

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I took a photo of my extra carbs to show the brass piece directly under the needle in the throat.
Maybe it would come out upward if it has a loose fit. ???
 

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Discussion Starter #10
Thanks. On a vt1100 it's not removable but I'll check if it's still there. Thnx.

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Discussion Starter #11
Piece is there. So back to square one. I still have no clue!

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I'll be following this thread. Similar problem with mine. Except, mine does get hot. Temperature doesn't seem to be a factor on mine though. Just at random times, no spark on front or rear cylinder. I've had it running for a half hour then it quit, other times 5 minutes. Whether the Temp gauge reads zero or half way, or anything in between, it makes no difference. When it first starts, it runs great on front cyl, and rough on rear, occasionally backfiring/misfiring on the rear cyl. Eventually, if it stays running, they both fire in harmony.
 
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