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Bogging in mid range

  • Thread starter Thread starter 2Stroke
  • Start date Start date
2

2Stroke

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On my 1980 GS750E I put on K&N individual filters and jetted the carbs to stage 3. I also raised the needle and drilled the hole on the top of the slide. I then put in new NGK plugs gapped at 28.

At low RPMs it runs great and great power. When I get up to about 4000 RPMs I am noticing it is bogging. If I pull the choke about half way out it takes off.

Does this mean that I am not getting enough gas?

What can I do to correct this issue?


Thanks in advance,

2Stroke :onthego::onthego::onthego::onthego:
 
2Stroke said:
On my 1980 GS750E I put on K&N individual filters and jetted the carbs to stage 3. I also raised the needle and drilled the hole on the top of the slide. I then put in new NGK plugs gapped at 28.

At low RPMs it runs great and great power. When I get up to about 4000 RPMs I am noticing it is bogging. If I pull the choke about half way out it takes off.

Does this mean that I am not getting enough gas?
Click to expand...

Yes

2Stroke said:
What can I do to correct this issue?
Click to expand...

Give it more gas.
 
Hey Kent,

I just filled it up. (joking)

What I need to know is should I increase the jet size or raise the needle some more?

Thanks
 
How much throttle was this bogging at?

Wide open go bigger main.

Part throttle, raise the needle.
 
It is on fairly rapid acceleration at mid range so I guess I will raise the needles.


Thanks,

2Stroke :onthego::onthego::onthego::onthego:
 
Yeah you're on your own then. Bogging at 1/4 or 1/2 throttles is a needle thing. Bogging if you hold it wide open and that's a main jet thing. But really before you change anything spend some time reading, how to tune Mikunis is old stuff, the information is out there.
 
Thank you for the replies.

Tomorrow I am going to adjust the needles as see what happens.

I have also been reading about doing plug readings so I may do that as well.

2Stroke :onthego::onthego::onthego::onthego:
 
On BS carbs start with the main jet, get it right first as it effects the lower power mixtures too. Always perfect the main jet first on them. But really read about it first.
 
Yes, Mikuni 32 BS carbs are the ones I'm talking about. CV carbs. Main jets first.
 
Ok

I got two larger jets when I ordered my Six Sigma kit because I told them I was planning on getting a pipe. I have not got that yet so at this point it is just individual air filters and the other adjustments I mentioned earlier.

Do you think I should go ahead and put in the larger mains and see if that takes care of the bogging?


Thanks,

2Stoke
 
Yes, then fine tune the needle, pilot jet, and mixture screws.

Just follow Mikuni's procedure.
 
Ok

I will let you know how it goes.


Thanks,

2Stroke :onthego::onthego::onthego::onthego:
 
I wouldn't do it until I got the pipe. To much time and effort wasted to want to do it all twice.. Just slap the bigger main jets in it for now and go get the pipe.
 
I will be a few months before I get the pipe but I may take your advice on just doing the mains. That is where I am starting anyway so if it runs okay that may do for now.

I am currently getting it ready to paint as well as doing what I can to lighten it up. I am also throwing around the idea of smaller seat.


Thanks again,

2Stroke :onthego::onthego::onthego::onthego:
 
Hey Kent,

I changed the main jets and the flat spot is gone. I took my first attempt at mixture and sync but will be doing it again because I think they both could be adjusted better.

I think I can still get a little more pep out of it on acceleration but it is doing a lot better.

Thanks again for your help.


2Stroke :onthego::onthego::onthego::onthego:
 
Last edited:
I got the bike on the highway today and it is bogging when approaching top speeds.

Right now I have 140s on the outside cylinders and 145s on the middle ones.

Should I get the next step up?


Thanks,

2Stroke :onthego::onthego::onthego::onthego:
 
What is the largest jet sizes you have used on GS750? Should I go to the 150s in the middle?


Thanks,

2Stroke
 
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