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Fouling plugs?...

Dpratt23

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Hey guys, new to the site, also new to the cycle world. I'm having a problem fouling plugs. A little background. Bought a 1975 cb750 (k2 I believe). Running straight headers w/pods. Plugs are fouling after about 1-2 miles. I believe it's running rich, black carbon. Tried running a hotter plug and have messed with the air mixture screws to no avail. I'm guessing I need to rejet down. A little insight would be greatly appreciated
 
See what you have for jets in it now. Make sure plugs are gapped correct and that your point gap and timing are set to spec. Are the pods over oiled? Are all 4 plugs black? And if it is a 1975 then it is a K5 for future reference.
 
First off, I'd like to confirm whether or not this is a bike you bought from me in Hoopeston. Blue tank, very nice stock side covers, like new tool kit, 4-2 pipes with baffles. Is that the bike?

Like dirtdigger asked, all four plugs, or just a couple (maybe 1 & 4 or 2 & 3) ?
You indicate that you're running straight header pipes... just header pipes with the mufflers cut off or similar?
1-2 miles isn't very far, obviously... is there much idling before riding? Low RPM riding only? Any power when you start the ride?
What have you done to the bike mechanically since you got it... basically just change the pipes, coils or wires, electrical changes?
 
First off, I'd like to confirm whether or not this is a bike you bought from me in Hoopeston. Blue tank, very nice stock side covers, like new tool kit, 4-2 pipes with baffles. Is that the bike?

Like dirtdigger asked, all four plugs, or just a couple (maybe 1 & 4 or 2 & 3) ?
You indicate that you're running straight header pipes... just header pipes with the mufflers cut off or similar?
1-2 miles isn't very far, obviously... is there much idling before riding? Low RPM riding only? Any power when you start the ride?
What have you done to the bike mechanically since you got it... basically just change the pipes, coils or wires, electrical changes?

Yes, this is the bike. Seems to be all four plugs, even though #3 is a little less fouled than the other 3. Running straight headers,no pipes or baffles.No electrical work done outside of pulling out wires that I don't need(rear turns etc.) Mostly low rpm idling, just around the neighborhood, if I ramp it up a little fouls quicker. Probably should pull carbs off anyway to give them a good cleaning, and to see what jets I'm running.Do you recall what they are?
 
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Well I'm sure disappointed that you're having issues. I assume the jets are stock, but don't know for a fact.

I had ridden the bike 80-90 miles over a 3-day period just before you picked it up. It ran well and seemed to improve each day, but I was on the road and running usually 45-55 and the RPMs were higher, of course, than at idle. I did plug chops and the plugs were actually pretty good with a tanish color, but at idle they turned more black.

My recommendation is that you clean the plugs and without idling for any length of time, get the bike on the road and keep the RPMs up to see how it performs. I'm not surprised that it doesn't run well with pods and header pipes only, but being rich does surprise me... I'd expect it to be lean. On the other hand, I'm not a "carb man", so depend heavily on what I've read rather than actual experience.

I'll be happy to tide over to your place and try to help if I can.
 
No worries. I'm not disappointed with the purchase in the least bit. I figured pulling the mufflers off would cause some issues, just trying to get it narrowed down. I appreciate the offer of coming down, but don't think it's necessary at this point. Have got a neighbor that I just met that seems to know his way around carbs, said he would help me break them down and give them a good cleaning, possibly change jets. Shoot you some pics soon. Won't recognize it though:)
 
Well I'm certainly glad that you aren't disappointed with the bike, but I'd still like to help you get it running like you want if I can and if you need the help.

I'mconfused as to why it would be running rich since I assume it has stock carb jets and with the muflers and baffles gone, and with the pods, I'd expect i to run lean. The only way I'd expect rich would be with the choke closed. But then again, I don't have the carb experience I'd like to have.

I did have a thought though, scary as it might seem. If due to some stupid mistake when I last cleaned those carbs I didn't get he jets tight and they fell out... that could cause a rich condition I suppose (just thnking out loud here, and wondering). Or if the needle clips are too low that could cause rich. Either way, I wouldn't expect it at idle, but at high RPM.

Regardless, with pods and header only, the carbs will no doubt need rejetted and nedle clips moved. You'll likely be doing plug chops and reading the plugs to get them set correctly, but you naturally have to get the bike running well enough to do the required checks.

I suppose the first thing to do is check the carbs for jets installed correctly and the sizes, as well as the needle clip positions.

In the end, keep in mind that although I won't be the best help, I'm willing to try... and I have another set of carbs I'll trade for the ones on the bike if it comes to that, but I don't think that will be necessary.
 
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