Carb Syncing - my method - cures running on just 1 cyclinder

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

I have noticed a number of postings where people say their bike runs only on one cylinder. Now on newer 650's with just one coil -
it can be:
A bad spark plug
Bad plug wire or end.
It can't be a bad coil or TCI unit - because if it fires on one cyinder it is firing on the other - since they both fire together.

What I did discover was a 3rd cause - Carb sync so far off that only one cylindar is doing any work at idle. The dead cylinder is usually not getting any air - so it doesn't fire. Remember you need spark, fuel and air to run.

To sync them up:
1) I first get them in the neighborhood with a visual adjustment with the carbs off the bike - watching the butterflies as I adjust the sync screw to make them even.

2) then with them on the bike - I start it up - and set idle at 1500+.
Then I pull each plug wire one at a time. The Rpms should drop evenly - but both cylindars should be delivering about the same RPMs. If not screwing the sync screw in clockwise brings up RPMs on the right cylinder, counterclockwise brings up rpms on the left.

3) Once I have that close - I fine tune it with a vacum gauge. I pinch the tube down on the vacum gauge - to limit the needle shutter to +/- 1 mark.
You can also use the clear tube method listed in other posts.

y bike seems to like to be at 10 on the vacuum gauge on each cylinder - when it is - they seem synced.

Once again when done - pull each plug wire one at a time and compare the rpms - they should be even.

Keep it in mind
hope it helps

Jim

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