uh crap lil bit of oil on plug!

Decided to tune up the bobber a bit, so saturday I went thru the carbs getting them nice and clean again. I installed a new inline, petcock filter, did an oil change and installed new plug caps(thanks chacal).


Ran like a dream on the way home and parked for the night. I figured I should do a sync just in case, rd it for about 10 min no problems in the morning. Parked it hooked up my carbtune and when I restarted it started right up and idled like usual but The #1 cylinder was running cold and back firing. I pulled the plug and a slight coat of oil was on the plug. (after noticing the po had a helicoil in there that had slid way down but managed to get it out and a new one in just before the rain.)


I searched I looks like Im looking at some serious work now? I dont want to start it to see if its fine now cus Im afraid Ill screw the engine up worse...the riding season has just begun too.

Am I looking at a top end rebuild, just rings? Might I get lucky if I go start her up? Thanks guys.

 

Compression test is in order. Rings or valves could cause oil. Try checking your compression dry and wet - that will at least be a starting point.

 

ok Ill get that done soon as I can get a gauge...I am correct in not riding right?

 

So could a deteriorated valve stem seal, a MUCH less expensive repair, and not "mission critical" (you won't blow the bike up riding it.) The compression test should give you some answers.

 

I wouldn't ride it until I got the compression done. Then you have an idea Rings or valves. As Fitz says valves not a huge deal but needs to be taken care of - rings you need to fix for sure.

 

Thanks guys, been reading up on both on here and in the manual. Im not going to move it until I get the test done.

It definitely sounds like a chore to do rings and valves not to mention costly.


Ill let you guys know my results soon as I can get them.

 

I finished the compression test looking like rings...

1- 80 Dry 153 Wet

2- 145 D 150 W

3- 140 D 170 W (may have went a bit heavy with the oil)

4-142 D 155 W

Also before the test I that the helicoil (po installed) on this cylinder had spun down and was about 1/4-3/8inch past the original end of threads, so now Im thinking bent valve too.

I want to fix it but got a decent amount in already, broke, and thinking Id have a lot of work ahead of me.

Then again it is my only bike and like the idea of doing a top end job to gain more experience. What you guys think rings and maybe bent valve? Worth the rebuild?

 

Damn it! I forgot to hold the throttle open while doing it, think I should retest or go with these numbers?

 

RETEST

Without the throttle OPEN, the cylinder can only draw off the air in the carb, and it can't get enough. So in escense, when the cylinder goes DOWN, it's creating a 'low pressure zone' in the cylinder. Then when it compresses, you are SUPPOSED to be creating a high pressure zone, but it can't get much higher than standard atmospheric pressure because it was below atmospheric pressure to begin with (the low pressure zone)

Open up the throttle and retest. Your numbers should go quite a bit up.
Will also give you MUCH better numbers as far as knowing what is what and what is 'broken'.

LEN!!! How'd I do, with the low pressure/high pressure, eh?!

 

I'd retest - to be honest I don't think they will come up much more than 10 from my own experience doing the same thing but they may. The 80 even without WOT is low.

I'm not sure why you suspect a bent valve. I'm not sure how the heilcoil would do that. The threads should not have gone beyond the plug and should not have interfered with the valves. At worst it would have hit the piston?

 

I retested got 85 dry and 150 wet with WOT.

Checked spark thats good.

Im convinced its rings from what ive read on here.

It still starts right up and idles well how bad is it to run like this off 3 cylinders really. Missing a big bike ride and bbq today, but if I did ride what kind of more damage am I looking at?

thanks guys