Exhaust temp, Carb synch

Here's an observation of mine from the last couple of days. Something to file in the "Diagnostic file"

After installing my UFO exhaust out of curiousity I used an infrared thermal gun (left over from my car drag racing days to check tire temps) to check the pipe temps on all four pipes a couple of inches after exiting the head.

The left side was around 240 degrees and the right side was around 130 degrees. This is at idle fully warmed up.

I of course say WTF??? and start trying to figure out why. I know all cylinders are firing and the bike was running great.

I took it over to a buddies of mine and put his synch guages on it and found out 1 & 2 are pretty close together and so were 3 & 4 but the left side was way out of synch to the right side

After synching the carbs all four pipes are right around 180 degrees at idle. Bike runs better also.

Something to remember......

Interesting indeed. The #2 carb is "fixed" so syncing shouldn't have made a difference in that cylinders temperature.

maleko89 said:

Interesting indeed. The #2 carb is "fixed" so syncing shouldn't have made a difference in that cylinders temperature.

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I agree, the final temp I believe was a product of resetting the idle speed screw after synching. The thing I was mostly seeing was that synching them pulled them all into line with each other. Seems as though 3 and 4 were either way ahead or way behind each other in regards to how far the butterflys were open when against the idle speed sadjustment knob.

The other thing that got my attention having done this the first time was how sensitive the adjustment screws are. Seems as a much finer thread adjustment screw would enable these carbs to more easily stay in synch??

i have noticed this on my bike too, one side running hotter than the other, i havent been able to check my synch yet however, still waiting on a merc refill. Hope it is as simple as synching them tho!

wfcall said:

I agree, the final temp I believe was a product of resetting the idle speed screw after synching. The thing I was mostly seeing was that synching them pulled them all into line with each other. Seems as though 3 and 4 were either way ahead or way behind each other in regards to how far the butterflys were open when against the idle speed sadjustment knob.

The other thing that got my attention having done this the first time was how sensitive the adjustment screws are. Seems as a much finer thread adjustment screw would enable these carbs to more easily stay in synch??

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Hey speaking of sync, What's a good carb sync to get? I need to add one to my todo list.

got me :confused2:

some guy on the ZRX board gave me his motion pro set, but i still need to get merc for them, i would get the stick or gauge type if i was buying new though, mercury is a pain and it freaks the better half out, lol

82ndCowboy said:

Hey speaking of sync, What's a good carb sync to get? I need to add one to my todo list.

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I have and use the carbtune II
I like it....no mercury to worry about.
BUT....stay away from their colortune.....I have one and think it sucks!
(but if you MUST get one....I'll sell you mine.... 1/2 price....used 1 time....lol)

I'm using the vac gages because I'm used to them since 1970. They are easy to check for accuracy by hooking them all up to one carb and then can be adjusted easily. They last forever and are reasonable to buy and work with.

bmannon said:

i have noticed this on my bike too, one side running hotter than the other, i havent been able to check my synch yet however, still waiting on a merc refill. Hope it is as simple as synching them tho!

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If you have the stock exhaust it's a little more difficult to get meaningful temp readings. The front pipes are double wall and the back pipes have that big adapter thingie and then they're single wall.....