Cool pipe

Hello, I have run my engine a few times and it seems to run well but when I measured the exhaust pipes I noticed #2 was cooler than the rest by about 45 degrees. I have cleaned d the carbs and the compression was right at 180 across the board. Am I just being overly finicky or should I wait and take it out and remeasure it before I draw the wrong conclusions?

Here's just a shot in the dark.

I wonder if it's possible that #2 is running richer than the other cylinders, and if that is causing it to run cooler. If you have a vacuum operated petcock there will be a vacuum line running from the petcock to the #2 carb. When the engine is running the vacuum from #2 carb draws on a diaphragm in the petcock which then permits fuel to flow through the fuel supply line(s). If that diaphragm fails or tears fuel can be drawn through the vacuum line into the #2 carb intake throat which can make #2 cylinder run rich.

If you have a vacuum operated petcock I suggest you try this; run the bike a bit then pull the petcock vacuum line off the #2 carb. See if there appears to be any fuel in that line; there shouldn't be. If there is, you should rebuild or replace the petcock and see if the pipe temperature changes.

Ed

Did you vacuum sync the carbs yet?

You could read plugs

Hadn't thought of that. I will try that next time I run her. Thanks, Keith

Sorry guys, still trying to navigate and communicate. So, I haven't synced the carbs yet. I did adjust the idle screws but the change was really hard to notice. PO told me he had a local shop spend a "really long time" getting them right for him. It didn't look to me like they drilled and replaced the plugs for them. Three were fully closed. I have them open approximately 2 turns each and no noticeable change still responsive but I don't know if that will change under load since I haven't been able to ride it yet. The vacuum petcock idea I will check. Anyway, long winded story but I thank all of youfor the ideas and feedback. It is really helpful as always. Thanks again, Keith

what I would do would be check the spark plugs. that will give you a decent idea of the mixture in all of the cylinders. If no. 2 is different than the rest, that would give you an indication. I would also make or buy a vacuum sync. It shouldnt take more than a days work and its something that needs to be checked pretty often. Look it up and I bet youl find the number 2 may be off in some respect.

Good luck

I will do that today. More background, I did have it running and rode it down the driveway. Turned around and no power. Measured the pipes and #2 was not equally hot as the rest. Pulled the plug and it was not wet and looked unburned as well. I pulled the carbs off and cleaned inspected them again. Put in new float needles and seats. Reinstalled and when I took it down the driveway it pulled nicely. At that time I thought success so never measured the pipes afterward. Later I started it again and when measured I got the low measurement. Waiting on the chain so haven't been able to start it. I guess I could but didn't want to without complete reassembly. It is just nagging at me. I will be getting a carb sync tool to check it. The other thing that is a mystery is why the adjustment on the needles seemed to have such a minimal effect. Is it possible the shop that worked on the carbs synced them based on closed needles and now they are far enough off that there is little effect when adjusting the needles. Wow! That was wordy but as you can see this has been ongoing. I have not worked on multiple carb setups before but have been reading the forum a lot and that has guided me through this. I'm not sure if I am reading these variables right or not. Now you know all I know....thanks Keith

Did you check the valve gaps?

I haven't checked them. Well, that is my itch to ride not letting me think straight! I will do that and see if that is the issue. I probably should already have done it by now since the bike hasn't been on the road in a decade. Thanks for all the advice it gives me several good things to look at. Keith