A couple of things

cathalp · Posted: June 17, 2009, 8:00 pm Post subject: A couple of things

Just got my '81 Special back together. Seems to be running fine apart from a pop in the left cylinder. The thing is, both cylinders seem to be running fine, but when I disconnect the right plug lead it stops dead. When I disconnect the left lead it labours,i.e. running on 1 like it should,there is a difference, so I know the left is firing, both pipes are hot. Is it something to do with the electronic ignition, which I doubt? Is it to do with the warnings I see about running this model with a dead cylinder without grounding the plug? HOw comes it runs on one side and not the other if this is the case?

Skip · Posted: June 19, 2009, 10:48 pm Post subject: Re: A couple of things

Hey Cathalp ,This is a great post which I saved which should be of help to you.Remember to ground the un-plugged spark plug wire.I have a extra spark plug I use with a pig tail ground wire to avoid damage to the ignitor.Also you could swap the plug wires to see if the problem switches sides.If it does you have a spark plug wire/resistor cap issue.But I think jimdi post is where you are going to find your problem.I went through this with mine and now with the idle up at 1500 rpm each cylinder will carry the other at 1100 rpm per side and with this my ATF carb stick has the carbs equal.
Good Luck
Skip

jimdi
650Rider Supporter

Joined: Oct 26, 2005
Posts: 509

Posted: Tue/Sep/2006 Post subject: Carb Syncing - my method - cures running on just 1 cyclinder

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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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