Cylinder firing too hot

[ejdirin]

Took the bike out into the driveway to fire up today. It started up with no problem. After running it for a while, I noticed I would get a flame from the left cylinder often and the left head pipe was getting extremely hot. The pipe was actually turning orange!

The engine is a 79 xs650 with the pamco electronic ignition and the "green monster" high output coils. Its a chopper project and has fairly short pipes compared to stock (2-into-1 pipes from mikesxs with the 2-into-1 replaced with 2 short slash cut mufflers). I hadn't noticed this problem before, although the left pipe was slightly more discolored then the right.

Any suggestions? Is it just that one side is running lean? Hopefully some that won't require dropping the motor from the frame....

 

[BigJimmyW13]

Whenever mine was firing exceptionally hot it was b/c the right cylinder was super lean.

 

[gggGary]

is that exhaust valve closing?

 

[Sundie]

have you rejetted your carbs for the open pipes and intake?

 

[ejdirin]

The valves seemed to be working fine when we last had the heads off.

Never did rejet the carbs for the new pipes. But I'm wondering why only one cylinder is firing so hot? You'd think both would be hot if the jets were off.

 

[Sundie]

Did you clean the carbs? Verify that some P.O. hasn't mismatched the jets? Verify all passages were open and flowing? That the floats were at a proper level?... Etc etc etc etc etc etc.

 

[xstwin]

You might want to take a look at the plugs and see what's up,they might be able to tell you something

 

[ejdirin]

Thats exactly what my next step was gonna be. I think the plugs were actually a little sooty from prior use (before pod filters, new pipes, new rings, etc). I was thinking of cleaning them off and then running it for a little while to see what they look like. How long should I run it to get a good idea? If its lean, it should be discolored, but not sooty, correct?

I was even thinking of getting one of these....probably overkill, but looks cool....

 

[ejdirin]

Ok. So I was running the bike last night. I adjusted the idle mixture and it seems to be running better. The only issue is that I had to bring the mix screw out about 4 or 5 turns, so I don't think it's spring loaded anymore. I think that means I need to change the pilots.

The other issue is that I was running it with a temporary gas tank and I could literally see the gas being consumed. It would go down the tube pretty quickly. I definitely lost significant mileage.

I have aftermarket pod filters, stubby mufflers, and I'm using a gravity-fed petcock (http://www.650motorcycles.com/Petcock.html).

Rejetting carbs is foreign territory to me. Any suggestions on where to start or why I'm having this problem? Thanks in advance!

 

[xsjohn]

4 or 5 turns........Remembering that we are on the pilot jets (mix screws) most of the time until we accelerate.......sounds to me like the pilot circuit needs a good cleaning....and that the PO didn't do something strange...........float height ....needle clip position....jets ect..........

xsjohn

 

[ejdirin]

Thanks xsjohn. So you think the only reason I had to come out that many turns is because the pilot circuit is junky in both carbs? Would that make the gas consumption skyrocket at idle speeds like that? What do you think about the fact that I have the pod filters and short pipes? I've attached a picture of the pipes too. Sorry about all the questions...I'm a carb novice.

 

[xsjohn]

As for the pods and pipes.....usually just the next sized MJ is all ..........but cleaning the carbs should be the next step ........using a small guitar string to probe the 3 tiny holes in the throat and blowing cleaner back and forth and using air .........and checking what jets you have and float settings so you can get a base line....then decide if things need changing............

xsjohn