1999 FXDX Chasing Blow By
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Tourer
Joined: Mar 2014
Posts: 452
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From: Northford, CT
No more than 10 psi difference between the 2 cylinders I thought?
Last edited by garystaven88; Mar 18, 2024 at 06:03 PM.
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From: poway
Sad to see the compression test results. After another good ride today I came home and did a compression test. Engine hot. Throttle wide open. Cranked until the readings stabilized:
190 psi Rear
175 psi Front
Adding oil to the front cylinder brings the reading up to about 200 psi
I am surprised how well the bike runs (minus the blow by) with those readings. Both plugs look fine/not oil fouled.
The gamble to buying a bike modded with no paperwork.
I bought it with 5k. It now has 14k. Someone was in the motor due to the Andrews cams. I suspect higher compression as well since hot starts sometimes cause a kickback (retarding the Fireball 1 degree helped).
Still has the stock tensioner setup.... may be looking into a 95" kit sooner than I thought....
I am going to try getting a scope into the cylinder to investigate further.
190 psi Rear
175 psi Front
Adding oil to the front cylinder brings the reading up to about 200 psi
I am surprised how well the bike runs (minus the blow by) with those readings. Both plugs look fine/not oil fouled.
The gamble to buying a bike modded with no paperwork.
I bought it with 5k. It now has 14k. Someone was in the motor due to the Andrews cams. I suspect higher compression as well since hot starts sometimes cause a kickback (retarding the Fireball 1 degree helped).
Still has the stock tensioner setup.... may be looking into a 95" kit sooner than I thought....
I am going to try getting a scope into the cylinder to investigate further.
With that CCP, I'd bet you have a bore kit in it also.. What curves are you running?
I'm with Dan, toss that catch.. If it still drips you can try larger drain back holes.
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Tourer
Joined: Mar 2014
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Likes: 228
From: Northford, CT
I noticed a hint of spark knock pulling from a dig at WOT.... plus the hot start kickback. I went to curve 4 and initial -1. No more kickback and I don't hear detonation. I set the limiter to 6200.
This engine really should have compression releases. If I pull the plug wires and try to start it continuously it will kickback and grind. Initial curve to -1 works fine since the motor fires right off. I am going to try a higher CCA Lithium battery I have in the garage.
So the more than 10 psi difference between the cylinders is OK?
Last edited by garystaven88; Mar 18, 2024 at 06:54 PM.
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From: poway
When I got the bike whatever clown tuned the Fireball before me set the limiter to 7500 RPM.... advance curve 5 (comparable to a stockish curve) and initial timing 0.
I noticed a hint of spark knock pulling from a dig at WOT.... plus the hot start kickback. I went to curve 4 and initial -1. No more kickback and I don't hear detonation. I set the limiter to 6200.
I noticed a hint of spark knock pulling from a dig at WOT.... plus the hot start kickback. I went to curve 4 and initial -1. No more kickback and I don't hear detonation. I set the limiter to 6200.
Yeah, I'd back off to 3 and -2. Just because you don't hear the ping doesn't mean the timing is optimum. It wouldn't surprise me that if you look inside the cylinders you see scratches on the rear facing walls.. Can you tell if it has Cometic head gaskets?
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Tourer
Joined: Mar 2014
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From: Northford, CT
Would those scratches be from timing being too advanced? I will check and see the head gaskets.
Thread Starter
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Tourer
Joined: Mar 2014
Posts: 452
Likes: 228
From: Northford, CT
Ah ok I see that now in the manual. I figured on a v-Twin you would want both cylinders to be pretty close to each other.
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From: poway
Too much timing, too much fuel.. You'll probably have to lean it out..
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