72 xs2 bogs down and backfires out of carbs, out of ideas

Yes the revs are there in first and drop and bog in second as it starts to lose power… I will order new clutch plates and springs from EBay to install.

If the clutch is slipping ,,the revs increase at full throttle not drop down
If no gear in do you have normal operation rev increase ?
In first gear riding full rev range no problems ?
In second gear ,problems ?
Other gears problems ?

What happens if you pull in the clutch when it starts to lose power .
Is it the same going from first to Third if possible to do
 
If the clutch is slipping ,,the revs increase at full throttle not drop down
If no gear in do you have normal operation rev increase ?
In first gear riding full rev range no problems ?
In second gear ,problems ?
Other gears problems ?

What happens if you pull in the clutch when it starts to lose power .
Is it the same going from first to Third if possible to do
In neutral, it revs up like normal. In first gear as I ride, it is slow but revs high before the speed of the bike catches up. In second gear, it also revs high but is still a slow moving bike. Third gear same. Pulling in clutch and releasing helps bike speed, I can feel the clutch moving when I do so. Sorry for confusion.
 
In neutral, it revs up like normal. In first gear as I ride, it is slow but revs high before the speed of the bike catches up. In second gear, it also revs high but is still a slow moving bike. Third gear same. Pulling in clutch and releasing helps bike speed, I can feel the clutch moving when I do so. Sorry for confusion.
Well maybe the clutch slipping . I would adjust it first
Then wait a while for other here to chime in
Then Inspect the clutch for wear ..and if in doubt replace parts and springs .. be careful ordering so get the right setup there are at least 3 different
 
Got my clutch all set up, but my last carb settings now no longer work and I am running very lean, going to re jet and try again. No more feathering the clutch to build up speed though. Finally some progress! Thanks to all.
 
went through 3 jet sizes going up from 100 main 32 pilot to 130/35 then down to 110/40 The 100/32 is much too lean (bogging when throttle given) but the 110/40 is so rich she really struggles to start and run. Going to try 105 next but any suggestions for matching main/pilot jet in these carbs?
 
went through 3 jet sizes going up from 100 main 32 pilot to 130/35 then down to 110/40 The 100/32 is much too lean (bogging when throttle given) but the 110/40 is so rich she really struggles to start and run. Going to try 105 next but any suggestions for matching main/pilot jet in these carbs?
As a general rule, it's not a good idea to change the pilots and mains at the same time... unless of course you're a seasoned tuner... which I'm guessin' you're not. :wink2:

Also speaking generally, the pilot jet has control from idle to about 1/4 throttle. From 1/4 to 3/4 throttle, the slide and needle are in control, and from there to wide open throttle (WOT) is the main jet.

You need to pick a range and jet just that range. Back in the day when I was heavy into tuning VM carbs, we'd tune for wide open throttle first, then the pilot and the needle last. Reason was the main had the largest affect on the VM's. Not sure what carbs you have, but maybe start with the pilot. Get the bike running good at idle to 1/4 throttle. Once you have that sorted, leave the pilot alone! Move on to WOT with the main. Get that sorted and then play with the needle to get mid range sorted.
 
I have PWK 32’s, I just tested them with 105/35 jetting and I still get some bad bog around 3/4 throttle (rich bog) would I up the main to 110 then and leave the pilot alone then? It starts and runs perfect up to 3/4 throttle.
 
I have PWK 32’s, I just tested them with 105/35 jetting and I still get some bad bog around 3/4 throttle (rich bog) would I up the main to 110 then and leave the pilot alone then? It starts and runs perfect up to 3/4 throttle.
Yes, as I pointed out above, 3/4 and above is the mains circuit. Why would you change the pilot, which only cover up to 1/4 if it's running good in that range? Leave the pilot be.

No, if you think it's too rich at 3/4, why would you "up" the main to 110? If you're too rich, you need a smaller main, not larger.
 
More....

You say it's a rich bog. Try going down one size on the main. If it gets better but still bogs, go down another.
Conversely, if it gets worse when you drop the main one size, it means you guessed wrong and it's actually a lean bog. If that happens, go up on the main.

And jus' to repeat, leave the pilot jet be if it's good at idle and low speed.
 
More....

You say it's a rich bog. Try going down one size on the main. If it gets better but still bogs, go down another.
Conversely, if it gets worse when you drop the main one size, it means you guessed wrong and it's actually a lean bog. If that happens, go up on the main.

And jus' to repeat, leave the pilot jet be if it's good at idle and low speed.
Dropped down to a 100 main and test rode. Started and idled fine, and revved up all the way in neutral. Under load the bog seemed slightly better but I still can’t get out of 2nd and that is the leanest main jet I have right now. I am going to play with dropping the needle down and see what that does.

Also is there a way to test my clutch for slippage besides riding? I want to permanently remove that from the equation since I just replaced the springs. The clutch does not seem like it’s slipping when pulled in and out but it’s hard to tell going so slow.
 
That sounds fairly normal however I had a clutch where all the plates seemed fine. Everything spec’d out but the fiber plates were almost 50 yo so I swapped them out. Major improvement. That was my experience and I can’t say yours are the same but that helped my clutch tremendously. If yours is slipping I don’t know why it would cause bogging, seems like it would be revving if it was slipping.
 
That sounds fairly normal however I had a clutch where all the plates seemed fine. Everything spec’d out but the fiber plates were almost 50 yo so I swapped them out. Major improvement. That was my experience and I can’t say yours are the same but that helped my clutch tremendously. If yours is slipping I don’t know why it would cause bogging, seems like it would be revving if it was slipping.
Agreed, I just wanted to be sure. I would like to replace the fiber plates but can’t find them in stock right now (from mikes at least) though the old ones spec out fine and it is under 10k miles motor.

I will continue to play with the carbs then.
 
If you want to replace the fiber plates reach out to @gggGary. He usually has them.
IMG_3406.jpeg

Maybe I will, Looks like we had the same bike when it was new! If it wasn’t so beat up I would have kept her mostly stock.
 
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