Pipes glowing red common on these bikes?

[Pd1620]

Trying to get my Carb issues under control on the RFZ 125. I installed a VM22 style carb. Bike still idles high, I want to let it run and see if it drops after warming up, but the pipe gets glowing red hot after about 20 seconds. I read in a comment that that was normal, but I’ve never had that happen on any of my Jap bikes. So I’m assuming this is a lean condition. I contacted Apollo and they recommend I buy their VM24, wtf?

[Red Hawk]

Any chance you can post a picture of the spark plug tip, it does sound like a very lean condition. Lean enough for engine damage if you were to run it hard. Most likely you’ll need a rejetting of the carb. This isn’t hard to do.

[pete]

if the bike has a stainless exhaust and is sitting with the motor running the pipe can start to glow..thin stainless heats up very easly and with no air flow to help cool it...
but check to see if it is running lean..


..

[Pd1620]

Originally Posted by Red Hawk

Any chance you can post a picture of the spark plug tip, it does sound like a very lean condition. Lean enough for engine damage if you were to run it hard. Most likely you’ll need a rejetting of the carb. This isn’t hard to do.

Here is the plug, let me know what you think.
Just a heads up I went ahead and ordered the VM24 direct from Apollo motors. It idles better, but still has the glowing pipe issue, and is still running rough.

[Pd1620]

Plug

[Merlin]

Could we see the plug straight on from the spark end?

[Emerikol]

Looking at the ground strap on the spark plug it does seem to be running a little lean. I would get the exhaust on my DR650 to glow red when I would fill up with 100LL AvGas out at my local airport. A picture of the spark plug head-on will help read the plug a little better. PD, what elevation are you at? If you're over about 2,500' ASL, you're likely going to have to go up a size on your pilot and main jets in the carb. If you determine that you are running lean, then a set of jet drills from Amazon might be a good investment for you. The only down side to drilling jets is that it's impossible to go back down in size. I think that VM24 uses Mikuni jets. Thanks to the marvel of internet capitalism, Amazon has jet kits for those, too. You can just buy the kit with an assortment of jets and spend an afternoon tuning. The collective wisdom of the forum should have you fixed up in no time.

[JerryHawk250]

I'm seeing the same thing as Emerikol. The high idle alone will make the pipe glow. What pilot jet is in the new carb? Is it the same as the stock carb or smaller. Have you adjusted the idle mixture yet? I would lower the idle to about 1500 rpms and adjust the idle mixture first.

[Pd1620]

Here are more plug pics.

[Emerikol]

Yeah, that grey ash on the end of the ground strap (the bit that goes over the top of the electrode) indicates that you're running very lean. I would start by dialing in the idle timing and setting the valves, and then go up at least one jet size on the carb. When you take the jet out, there will be a number stamped into the face. That's your jet size. You can use that as a base point to start your tuning adventures. When you order new jets, you should probably order an adjustable needle, too. Here's a really good write-up on how to tune the carburetor:
https://www.sscycle.com/tech-info/in...rb-quick-guide