Secondary jets

[lee_dohc]

Hi guys,

Need a little advice, struggling to get a 83 cb750 running correctly. Recently rebuilt motor, valve clearances all correct etc, carbs have been cleaned and rebuilt the bike was actually running pretty well but not perfect (it's a friend's bike) removed the carbs to check everything was in order it was all good apart from it was missing the secondary jets.. I put them in now it's running even worse!! Any ideas?

Thanks

 

[brettp]

Using pods or stock airbox?
Are the carbs synced?
Are the mixture screws all set the same?

 

[lee_dohc]

Using pods, although currently not fitted as I wanted to see what was happing from the back.. yep all balanced all screws correct. Just odd it ran okish with no secondary jets

 

[lee_dohc]

With all the correct jets fitted it kind of runs on idle but as soon as you cracked the throttle it wants to die

 

[brettp]

Pods are notorious for covering air circuits needed by carbs inlet side.

 

[Loose Chain]

With all the correct jets fitted it kind of runs on idle but as soon as you cracked the throttle it wants to die

When you say "all the correct jets" what do you mean? What jets are they? Sizes? Why are you running it with no filters?

 

[lee_dohc]

68 and 102.. I've got the filters off just so I can look into the carbs to check the slides are not getting stuck.. its the same with the filters on

 

[Motogrady]

Try putting the filters back on, take black electric tape and blank off half of each pod,
restrict some intake airflow.

 

[Loose Chain]

If you are planning to use individual pod style air filters you are going to need larger jets. 68 and 102 jets just barely get it done with stock airbox and stock exhaust. Running it with no filters at all is even worse. So if you really want pod filters you are going to need larger jets.

 

[lee_dohc]

If you are planning to use individual pod style air filters you are going to need larger jets. 68 and 102 jets just barely get it done with stock airbox and stock exhaust. Running it with no filters at all is even worse. So if you really want pod filters you are going to need larger jets.

That will explain why it runs better with no secondary jet haha

 

[Loose Chain]

Did you do the rebuild on the carbs or did someone else do them? Don't assume they are good if you are going on the word of someone else. Carburetors not being properly rebuilt is a recurring theme around here.

 

[lee_dohc]

I've just pulled them apart and gone over them myself.. any recommendations on jet sizes?

 

[Motogrady]

I run 75/115 I believe.

This with 8 - 1/2 inch holes drilled in the underside of the stock airbox, stock paper filter, and a short 4/1 muffler.

Would be nice if you put up what works for you.