Temp difference between cylinders

grizld1

OK, xsjohn, you've got me curious enough to get serious.

For those who haven't been following the issue, John checked his cylinder temps with an infrared thermometer and found that the right gets hotter than the left by about 50* F. Every time others (myself included) have checked, they've gotten the same result. Ignition system isn't a factor--happens with points, OEM TCI, and Boyer. Happens with OEM and aftermarket exhausts. Happens with OEM and aftermarket cams. Happens with BS38's, BS34's, and VM roundslides. Happens with both stock and ported heads.

John's theory is that it's causing (caused by?) a power imbalance between cylinders that can be corrected by pouring more fuel to the right. What puzzles me is that I've neither seen nor heard reports of a higher incidence of piston holing/detonation, failure, valve burn, or premature wear on the right than on the left.

So--John's agreed to look into testing his theory on a dyno, and since I instigated him to do it it's only fair that I put some time and money behind the research too. Combustion temperature is what signifies, so in a few weeks there'll be a pair of probes hanging in my headers and a Westach double-needle EGT gauge in the instrument cluster. I think the cause is probably reduced right side heat dissipation due to the hot closed clutch cover, but we'll have some hard data to digest pretty soon.

John, we'll run this down if it harelips every cat in the country.

xsjohn · Last edited by xsjohn on January 30, 2008, 2:54 pm; edited 1 time in total

Dang Griz you didn't have to do that but I truly appreciate you looking at it....dumping more fuel to the right is a bit of a stretch.....a bit of fuel is more accurate......Would be interesting to see it the exhaust temps are higher also.......

put 100 miles on it yesterday 60 degrees or higher and could not find any temp discrepencies anywhere.....measured plugs.....heads.....cylinders......and intakes.....at least 5 times......I feel its ready for the dyno when it warms up enought to survive the trip..........

xsjohn

davidnj2

Hey guys,
really appreciate your covering this subject. i was beginning to think i might have a faulty intake boot or that the head gasket might be sucking air on that side. i'm runnig vm34's and have decided to fatten up the right side a bit. my stock piston did look like it had an ever so slight partial seizure. this inherant quirk is most likely the culprit. thanks again.

xsjohn · Last edited by xsjohn on January 30, 2008, 10:04 am; edited 1 time in total

Been there and done that.......don't know why 80 didnt sieze...one exit onthe express was allit was good for.......guessing I realized somethig was not quite right at first and never pushed it until I found out what was causing it.......tried tons of fixes until I came up with what I consider the better solution that I could find after fing with it for 8 years........never ending situation.......and other carbs too for that matter....send me a set of needles if you would like before you spend to much gray matter on the subject......

john

ghostyder

my first xs650 which is the one Im building right now came with a bent valve on the left facing forward sitting on the seat. It had 8,000 miles on the odometer.
I bought another engine off of e-bay, with 6,000 miles on it and the hopes that the seller was honest. Havent finished putting it together yet. All of this talk about one side running hotter than the other makes me nervous.

I figured I'd be alright because I got a great price on the basket, but I guess I wont know until I finish assembly. Wish I had heat in the shed.

xsjohn

ghostyder....These things have run for years......not to worry....run it........as for me and my rant....just think I have found some things maybe to make them run better.....only time will tell if I am right......sure has with mine......

John

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Yamaha xs650