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Fuel/air running too rich on my 750

  • Thread starter Thread starter gr333nyboy
  • Start date Start date
G

gr333nyboy

Guest
I've taken off the pods my bike after never really getting them to perform as they should, (ok I read it was a nightmare!) and now i've put on a stock airbox, new rubbers, all on fine, and there's an immediate improvement in performance. BUT its now blackening the plugs with carbon so this must be an over-rich mix right?

Now, the question: is there anything that can be done before the whole dismantling carbs and adjusting/rejetting thing? I know that has to be done, but I cant do that yet, so Im looking for a short term fix.

thanks
 
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gr333nyboy said:
Now, the question: is there anything that can be done before the whole dismantling carbs and adjusting/rejetting thing? I know that has to be done, but I cant do that yet, so Im looking for a short term fix.
Click to expand...
Yes, there is something that can be done.

First, give us a few clues. Like, what year is the bike? Yes, it matters, because they had different carbs, which means different adjustments.

Second, under what conditions are you noticing richness? Note that there are at least three separate circuits in the carbs that can be adjusted, which one Ior more) of them is making it run rich? From idle through 1/8 throttle, you will be dealing with the pilot circuit. From about 1/4 to almost 3/4 throttle, you will be dealing with the needle circuit. From 3/4 to full throttle, you will be dealing with the main jet. You need to do "plug chops" to test each of these circuits to see which one is causing the problems.

Third, you mentioned removing pods, so you KNOW you will have to re-jet back to stock (unless you also have a pipe on there). However, most of the jetting for the pods is done in the main jet, so if you avoid full-throttle application, you can probably limp by for a while. Depending on the type of carbs (what year?), you can tweak the pilot mixture a bit. Again, depending on the type of carbs, you can probably change the needle height for the mid-range without pulling the carbs.

.
 
I have same problem my bike :D too rich..idle is good and full thottle...but driving stedy 80km/h it's starts like choking:confused: main jet is 110 and air is 140..i have all so try katana jets and they are like 115 and 160...choking thing started when i cleaned carbs..fuel level is fine...so i drop needels now and hope it helps...plug chop :D never heard or try that before..have to try that next summer :D :D
 
P.V_FINLAND said:
I have same problem my bike :D too rich..idle is good and full thottle...but driving stedy 80km/h it's starts like choking:confused: main jet is 110 and air is 140..i have all so try katana jets and they are like 115 and 160...choking thing started when i cleaned carbs..fuel level is fine...so i drop needels now and hope it helps...plug chop :D never heard or try that before..have to try that next summer :D :D
Click to expand...
No idea how close your jetting might be, we would need some clues from you, too.

Mainly ... what bike are you talking about?
icon_shrug.gif.pagespeed.ce.N04XKu56YJ.gif


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If it's a 1980 or later 750, take the airbox lid off. If it's a '79 or earlier, not so much.
 
Its a '78 750e. I'm assuming theyre the original carbs, they look right to me, but can't be sure.

Yes, it'll need rejetting, but i can't do it yet. I cleaned the plugs up before the airbox went on (they had carbon even then) and its black again around the tip of the plugs, and reading what i have, changing from pods to stock means an over-rich mix? It runs pretty well, there are no 'bands' where its suddenly struggling (in fact its a BIG improvement on the pods) but it obviously isn't yet right.
 
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Thanks for the update. If you put that information in your sig, we won't have to ask you every time you ask a question (and you can be SURE that we won't remember it :p).

Any idea what your screw settings are on the carbs right now? For a basically stock setup, the fuel screws (the ones on the bottom of the carbs) should be out about 3/4 to 7/8 turn from lightly-seated. The air screws (the ones on the sides of the carbs) should be about double that, or 1 1/2 to 1 3/4 turns.

For the time being, until you can get the carbs off to do all your re-jetting, try turning the air screws out 1/4 to 1/2 turn to lean the pilot mixture a bit.

.
 
Thanks Steve, I shall have a look into this!
Much appreciated!
 
Steve said:
No idea how close your jetting might be, we would need some clues from you, too.

Mainly ... what bike are you talking about?
icon_shrug.gif.pagespeed.ce.N04XKu56YJ.gif


.
Click to expand...
It's a 650 with mucho miles! and apparently many replaced parts, much to my horror!
 
Thanks. Its a motad 4 into 1 which I was told rates as stock in terms of settings. Yes, the carbs will absolutely need getting into, but I cant do that yet, so i'm just looking to improve things until then.
 
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