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One cylinder sportster?

socalrebel

socalrebel

Member
I just bought a 89 XLH 883 from a lein sale. I am getting spark to both cylinders, but only the rear hole is firing good. It has a Mikuni Carb and I kinda think it's just pooring gas down the hole. The front plug is really wet. I don't have any history on the bike. The guy that owned it left it in a storage unit. It also back fires thru the carb. Any Ideas?
 
biglew55 said:
I had this happen on a sporty and a shovel and the coil was weak. It showed spark, but wasn't firing once cylinder under compression. If you have a Friend with one you could exchange temporarily, I would defiantly try that.
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And if that isn't defiant enough what will you do?:newsmile100: Seriously ,have you checked compression? Low compression will also cause non firing
 
I will give that a shot. I did take the plug out and check for spark. There was a lot of spark but not really a bright spark. This is my first Harley so i'm still green around the gills. Thanks man
 
I would definitely check the compression and go through the carb and check to make sure the jets are clear. They aren't that complicated.
 
I checked the compression. It is even in both holes. 90psi (not a great compression guage, but... My next step is to check the carb and clean it up. It sat for quite some time. That could very well be the prob. Thanks guys
 
Try a compression test with another gauge. The 90 lbs is about as low as it can get and still run.
 
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If the compression is that low with another gauge, try soaking down the cylinder with a couple of ounces of Marvel Mystry oil, let it soak for 24 hrs or so, crank it over with the plugs out, put them back and try to get it to run, then check copression again. Marvel is great for stuck rings.
 
Alot of people dodn,t realize when doing a compression test you have to hold the throttle wide open or it will read low try that then get back,jel
 
If you pull the plug to take a compression reading, then that cylinder is not firing anyway. So, there will be no further expansion of the rings to cause any increase in compression in that cylinder.
Now, If you could mearure compression while the cylinder is firing, and at maximum load, then you would be able to see the maximum pressure that cylinder is capable of holding.
Without any combustion or load, you will only see the pressure that cylinder will hold with the rings in their natural state.
Just the way I see it...
 
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