Compression Test Questions

[86FJNJ]

ok so for now as I try to get engine running without a fuel tank and just have an IV tube of gas hooked up to the carbs with no filter on the carbs I should cap off that little vent on cylinder 1?

In my first run test I believe I am running lean based on everyones feedback and what I looked up because it only ran with choke on and carbs are essentially stock and I have F1r slip ons and no filter on the carb.

I'm thinking if I hook up those carbs I got that are set up for a legend with the center fuel inlet and 120 main jets it should run better in this condition although then most likely on the rich side but then I should be able to get it to run without the choke on right?

[Pat Conlon]

I should cap off that little vent on cylinder 1?

Did you see my post? It's not a vent....

[86FJNJ]

I used the wrong term but I understand thanks for your explanation, right now I don't have a gas tank so I just capped the hole off and I threw the legends carbs I have on it and it fired right up with no choke and ran really well compared to few days ago when I tried running it with the stock carbs, the Cylinder 1 header is now hot so I believe capping that hole on the intake of cylinder 1 did the trick to get cylinder 1 running. I now feel pretty confident that the engine runs well enough to take the next steps in getting the engine more dialed in which will be ordering the right jets and probably sending carbs to RPM for a thorough cleaning.

Bike smokes a lot but there is a lot of oil in the exhaust and in cylinders from me filling them with oil previously so I hope that burns off after a certain amount of time and I don't have any other issues. The oil in it is 10w-40 with about 5% marvel mystery oil so it is on the thin side but it's been about 25 degrees here in NJ so I felt that was appropriate for my purposes now.

[86FJNJ]

Update after 500 miles of riding, did another compression test yesterday:

Cylinder 1: Was 150 psi, still 150 psi.
Cylinder 2: Was 135 psi, now 140 psi.
Cylinder 3: Was 140 psi, now 145 psi.
Cylinder 4: Was 140 psi, still 140 psi.

Could these lower compression numbers be why I need to have my fuel screws further out so pilot circuit gets more fuel due to lower compression?

[Pat Conlon]

See? We told you...get some miles on that engine and your numbers will improve.

Congrats...Good compression numbers.

 The 7% compression variation (150/140) won't affect your idle settings.

 Get that rusty tank squared away. (Electrolysis and POR15)

'Till then, keep riding her!

Cheers

Pat

[86FJNJ]

Thanks! I still have the 1991 tank on it that really had no rust in it and I'll keep that prob for this season.

Reading through some other posts I see some mention of Yamaha Ring Free wondering if I should use that to help clean it out a bit.

[Pat Conlon]

Sure, give it a try, why not? I think you are over the hurdle, getting it running. Just keep riding, things will naturally loosen up.