Carbon build up in the exhaust port

CharlotteSpreeRider · Post by **CharlotteSpreeRider** » Sat Feb 23, 2008 9:19 pm

I finally got around to getting rings and a gasket set for my 85 Spree today. I pulled off the head and jug, then the piston. The carbon build up on the exhaust port was so horrible that both the piston and the cylinder have nasty gouges on them starting at the exhaust port and going down. The head had a couple of spots with really bad carbon build up too. I happened to have a spare piston without gouges lying around, so I'm probably going to put that into the gouged cylinder. The Spree was getting up to 30 MPH no problem, but the compression was a little low. The exhaust gasket was so worn out that it just fell right off. I assume that it has been leaking for a long time.

Is there any good way to prevent the build up in the exhaust port from happening again? I might find a new jug, but then again, I might not bother since this one works well enough for me as it is.

-aseigler

hondaman · Post by **hondaman** » Sat Feb 23, 2008 9:50 pm

Dump whatever oil you have in there right now and replace it with clean 2 stroke injector oil , I repeat 2 stroke injector oil. Using any other oil causes that carbon build up you found much quicker.

CharlotteSpreeRider · Sat Feb 23, 2008 10:31 pm

Thanks, but I've been using Honda GN2 since I got this thing running in the summer. Knowing what I know now, I'd have pulled the thing apart way back then. The oil tank and lines have been replaced from when I got it. I wouldn't be surprised if the previous owner used chainsaw oil in it.

So bad oil is the usual suspect for excessive carbon build up?

Thanks,

-aseigler

uspmale · Post by **uspmale** » Sat Feb 23, 2008 11:34 pm

A leaky exhaust gasket can cause a lean condition as well.
gases not only leak out, but fresh air gets sucked back in on the return, thus causing scoring on the exhaust side of cylinder wall.

CharlotteSpreeRider · Sat Feb 23, 2008 11:38 pm

uspmale wrote:A leaky exhaust gasket can cause a lean condition as well.
gases not only leak out, but fresh air gets sucked back in on the return, thus causing scoring on the exhaust side of cylinder wall.

Wow, that sounds like my problem. The cylinder and piston are scored all to *, but only in the 1-inch strip below the exhaust port. The rest of the piston and cylinder are squeaky clean. How bad is it to run a good piston in the broken cylinder until I get around to getting a new jug?

Thanks,

-aseigler

Kenny_McCormic · Post by **Kenny_McCormic** » Sat Feb 23, 2008 11:55 pm

Find somebody with a drawer full of flex hones and rehone the jug.

uspmale · Post by **uspmale** » Sun Feb 24, 2008 3:41 am

Kenny is right.
A good proper honing can do wonders to a cylinder.
I've done it numerous times, with outstanding results.

Kenny_McCormic · Post by **Kenny_McCormic** » Sun Feb 24, 2008 9:39 am

uspmale wrote:Kenny is right.
A good proper honing can do wonders to a cylinder.
I've done it numerous times, with outstanding results.

Yea lemme go digout the pics.

This is a leafblower ran without the proper amount of oil.

Broke the ring getting it off cause it was melted on the piston.

Piston

If I had to guess I would say some of the scoring was .060 deep! We didnt have a flexhone small enough to fit the bore so we used a hone for a brake cylinder. i smoothed out the piston with sandpaper and filed out the ring grove. Put a new ring in, oiled the s*** out of everything and it RAN! That engine is still running and has good compression after a few hours of use.

uspmale · Post by **uspmale** » Sun Feb 24, 2008 11:26 am

Nice pics Kenny.
A picture says a thousand words.
Thanks

CharlotteSpreeRider · Post by **CharlotteSpreeRider** » Wed Feb 27, 2008 1:19 pm

Took jug to Honda dealer today who honed it in about 2 minutes with better results than I could have expected, for free. I'll find out how well it worked tomorrow, but it looks and feels REAL good.

-aseigler

chevyguyjay · Post by **chevyguyjay** » Wed Feb 27, 2008 11:50 pm

i went to sears a couple weeks ago and purchased a brake cylinder hone for $10.00 on clearance. it has your typical 3-stones. u can adjust it for more or less friction. it does wonders in doin a quick clean up on a cyinder.

CharlotteSpreeRider · Post by **CharlotteSpreeRider** » Thu Mar 06, 2008 4:18 pm

Got everything put together finally this afternoon. Compression was just over 100 PSI before, now it's almost 120 PSI. Top end is about the same, but boy howdy is it ever better on the take off. I can't wait to race the dude on the bicycle again...

-aseigler

itzmepete · Post by **itzmepete** » Fri Mar 07, 2008 1:55 pm

I wouldn't use another piston unless you fix that cylinder. Yes, SEARS sells a small brake coning cyinder kit. I would get that and some light oil, any light oil. Adjust the honer with light to medium presure, hone, oil wipe, hone oil wipe, checking it each time you wipe till you just see a criss cross x pattern. Don't hone fast and the pattern must be x shapped and not close. Hone all the way up and down. If the scorn marks are not deep, .010, it will clean up nice. In any event, if its deep, your best bet is to get a new piston, maybe over sized with rings. You will have to get it mic'd. After its honed, just run down to Napa and have the machinest mic it, they will do it for free. Then look at the specs and see if you are within tolerances or can go over sized piston. Me, I would hone it till its clean, use the good piston if it has no scorn marks , if it has light marks, wet sand it evenly under running water with like 800 grit to start and 2000 after that. Then use NEW rings, break in as usual. Read my post in technical preformance under title

SR50 Gear Ratio Teeth per Gear Question,New Honda Parts ebay

I did a mower, story there, compression went to almost new 170 pis I think. Was unreal and ran awesome.

Your ped is running now but your compression is no where near what it should be. You should have honed it, new rings and new head gasket as well as exhaust at the VERY LEAST.

CharlotteSpreeRider · Post by **CharlotteSpreeRider** » Fri Mar 07, 2008 3:31 pm

I had the Honda dealer fix the cylinder, and then I put in the good piston with new rings, new head and base gasket. 118 PSI is good for Spree motor.

-aseigler

itzmepete · Post by **itzmepete** » Fri Mar 07, 2008 9:56 pm

118 is that when the engine is cold or hot?