81 KZ750e wont rev past 7k

Ok so, update...

Put the 5/16 fuel filter in place. Took her out and opened her up on the freeway onramp. It was better. It was actually trying to accelerate this time. I think I found my issue. I think there still isn't enough fuel getting through this filter though because 5/16 is still smaller than 3/8 and don't forget the resistance the filter screen causes the fuel going through it. I took the petcock apart while I was in there and it was clean as a whistle.

The old inline filter had some fine sediment in it, so I can't go without a filter for now. If I get the time I'm going to remove and treat the tank with Milkstone remover to get rid of the rust inside, then after a couple dozen miles I can remove the filter and go for it.

Thanks so much for the suggestions, they led me in the right direction to solving my problem

Here's the fuel filter I use. It is small, it passes up to 6 gallons per minute, and it works great. I highly recommend it! Ed

www.kzrider.com/forum/3-carburetor/59406...ne-and-filter#633243

Awesome Ed, thank you so much! I'm going to scope it out.

Might also want to check that there are no kinks in your smaller line. Even gradual bends can close off the inside of the line. I had a similar issue and found I had far too much line... cut off a 1/4" and all was well.

Plus 1 on the timing advancer...Amazing how cruddy those things can get....don't need to remove points, &c to test....just slap a timing light on her and make sure she is advancing properly...
Also fuel tank cap vent can get clogged (they breathe through the keyhole) and if the tank can't let air in, it won't want to let fuel out...

OK quick run down of what i've checked/done so far:

-checked internal petcock filter and it was clean. Blew air through petcock to make sure it was clean. Tank was pretty free of any junk.

-changed fuel filter to high flow 5/16" inlet/outlet filter. Had a very slight improvement but still wont rev past 7.5k

-I pulled the advance cover and rotated the mechanical advance with my fingers. It felt smooth and I saw no rust inside. I did however see some fine metal shavings, looked like filings, clinging to the pickup blades. I wiped them off. Didn't see any evidence that the advance was hitting the pickups though. I will check it with my timing light next chance I get, it was late at night and my Kerker pipe would wake up the whole neighborhood!

-checking valve clearance- whats the procedure? I replaced the valve cover gasket and all I saw were hydraulic lifters. It's been a long time since i've worked on 4 strokes (2 smoker guy for years) but i thought hydraulic lifters didn't need valve adjustments?

Thanks guys!

I agree with Nessism that it sounds like a jetting issue. Even though you reported in first post that carbs were re jetted I would take any previous owners statement with a grain of salt.
Next time you have carbs off check jet size - might need magnifying glass. If your carbs are Keihin CV34 then stock jetting was primary mains 62 and secondary mains 125. When I had ^K&N pods and 4 into 1 exhaust I ran 62 and 135 and then later and better ran primary mains 70 and secondary mains 140.If your carbs are something else then please disregard.

Regarding valves - hydraulic lifters I wish. The cams rotate and press on the top of upturned bucket. Beneath the bucket is a shim and beneath the the shim is the valve stem. All known as ``shim under`bucket``. Checking clearances is not difficult but is best described in the manual.

So Mike, gotta ask to clarify... (and because I don't see where this was asked or answered)

- How long have you owned this bike? disregard, in your OP
- Has it always been this way for you, no rev over 7-7.5k since you bought it? If not, what did you do right before this problem started?

JR, thank you so much for the input on jetting... I will pull carbs and check. Also, I'm still trying to figure out where I can print the manual...

As for owning the bike, it's always been this way. Put on new emgo coils (black ones) because the old ones were all corroded and shot. It runs great since the coils it just won't rev. I don't think they are the issue though.

Would observe the advancer function under a timing light to watch for it to quickly move back and forth as rpm is varied by blipping the throttle.

Failure to advance will result in loss of power under load.

Good Fortune!

Thanks for the info Mike... yea, follow the jetting lead. Good luck...

Well, the long Siberan winter has finally lifted here in Ohio. :woohoo:

I pulled the bike out yesterday and checked the advance and timing- its operating properly and timing is spot on. I did have a little bit of popping both on the throttle and when letting off. This makes me suspect that the pilot circuit is lean at the very least.

I can pull the carbs when I have a day off, but my issue is that they were synced after they were cleaned recently and I dont wanna screw that up by pulling and disassembling them. I imagine that not making any adjustments will not change the sync? If I have to buy a carb synch tool and do it I will, but i'd rather not lol.

Patton wrote: Would observe the advancer function under a timing light to watch for it to quickly move back and forth as rpm is varied by blipping the throttle.

Failure to advance will result in loss of power under load.

Good Fortune!