EVO All Evo Model Discussion

Correct Combustion? Your Thoughts

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Old Apr 7, 2026 | 01:29 PM
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Default Correct Combustion? Your Thoughts

1990 EVO w/17k miles. Completely disassembled to reseal. Cylinders and rings were perfect. All new gaskets and seals. Factory CV rebuilt and has a 185 main and 48 slow jet with the mixture screw out 2.5 turns. Factory air cleaner with most of the back cut out and K&N filter. Stock head pipes and SE Slash Cut mufflers with no baffles. Bike runs excellent with no pinging whatsoever. I run 89 non-ethanol gas. The only issue is once in a while when it's idling and I crack the throttle, it will pop thru the carb. I sprayed brake cleaner around the intake to head gaskets and there is no vacuum leak. New plugs with 300 miles on them. Left=Front and Right=Rear. Thoughts?


 
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Old Apr 7, 2026 | 01:33 PM
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Double check your ignition timing, may be too far retarded. Also check the diaphragm in the carb for a pin hole or damage.
 
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Old Apr 7, 2026 | 01:43 PM
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That is choke smoke that has not burned off, but it almost has on the front.

Put 2 new plugs in, them remove them. Re-install the old ones, ride 10-15 miles and swap plugs. Ride 100+ miles, same day, then take a picture.
 
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Old Apr 7, 2026 | 02:32 PM
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Originally Posted by Ohio HD
Double check your ignition timing, may be too far retarded. Also check the diaphragm in the carb for a pin hole or damage.
Brand new rebuild kit with new diaphragm. I will check the timing as it was a bitch to set but I thought I got it correct. I also want to install a new vacuum line on the VOES.

Originally Posted by t150vej
That is choke smoke that has not burned off, but it almost has on the front.

Put 2 new plugs in, them remove them. Re-install the old ones, ride 10-15 miles and swap plugs. Ride 100+ miles, same day, then take a picture.
Doing this will eliminate the "choke smoke" on the plugs to get an accurate reading on the plugs when the bike is warmed up. Correct?
 

Last edited by BigMike; Apr 7, 2026 at 02:34 PM.
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Old Apr 7, 2026 | 02:33 PM
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Originally Posted by BigMike
Doing this will eliminate the "choke smoke" on the plugs to get an accurate reading on the plugs when the bike is warmed up. Correct?
Yes sir!
 
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Old Apr 7, 2026 | 03:49 PM
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I have MUCH better luck with an unlit propane torch around the intake checking for leaks. Plus it's cleaner too! I don't like brake cleaner anywhere near my paint.
 
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Old Apr 7, 2026 | 07:46 PM
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I never made an Evo run for **** without a real Exhaust...Hollow Mufflers do Not Count..
 
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Old Apr 7, 2026 | 08:59 PM
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I think the only thing left to do is install an S&S E so all of your dreams can come true. Then you could mess with the accelerator pump to fix that issue.
 
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Old Apr 7, 2026 | 09:55 PM
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Originally Posted by Rains2much
I think the only thing left to do is install an S&S E so all of your dreams can come true. Then you could mess with the accelerator pump to fix that issue.
Some of you S&S guys are as evangelical as the Amsoil guys. There's not a thing wrong with a properly tuned CV carburetor.
 
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Old Apr 8, 2026 | 05:08 AM
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Looks like there's shadowing on the rear plug, so hard to tell.. Front looks good.. Definitely need more timing.. on your cam position sensor you will see timing lines, rotate the CPS 2 lines clockwise and install new plugs like Rufus mentioned.. NGK BPR5ES-11
..
 
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