Engine Pegs Out

Hi guys, new here and making my first post. I have been a lurker for a while and enjoy reading.

I have had a 1978 KZ400 for a couple weeks now and it runs great. Such a fun bike. My problem started last night after it had been sitting for about 3 days.

It starts great, idles great, and runs from 0-20 great. Then the problem starts. When I shift into second gear and the bike hits about 20 MPH the engine sounds like it is governed or has hit a rev limiter, the acceleration stops, and I cannot go any faster. I shift to third gear and the same thing happens at 30 MPH.

When I say it sounds like it is governed/rev limiter, I mean that no matter how much I turn the throttle there is 0 response. The engine just revs up and then bounces. Don't know how else to describe it. Unfortunately, the PO took the tach off so I cannot tell you actual RPM numbers.

If you have any questions I will do my best to answer them. Any help or suggestions would be greatly appreciated.

txfirewarrior wrote: Hi guys, new here and making my first post. I have been a lurker for a while and enjoy reading.

I have had a 1978 KZ400 for a couple weeks now and it runs great. Such a fun bike. My problem started last night after it had been sitting for about 3 days.

It starts great, idles great, and runs from 0-20 great. Then the problem starts. When I shift into second gear and the bike hits about 20 MPH the engine sounds like it is governed or has hit a rev limiter, the acceleration stops, and I cannot go any faster. I shift to third gear and the same thing happens at 30 MPH.

When I say it sounds like it is governed/rev limiter, I mean that no matter how much I turn the throttle there is 0 response. The engine just revs up and then bounces. Don't know how else to describe it. Unfortunately, the PO took the tach off so I cannot tell you actual RPM numbers.

If you have any questions I will do my best to answer them. Any help or suggestions would be greatly appreciated.

Hello, txfirewarrior, and WELCOME to KZrider!

If not already done, would inspect the timing advancer to determine whether it's stuck in the retarded/closed/idle position.

Might need lubing and/or cleaning.

Good Fortune!

Does the engine RPM go up but the bikes does not go faster? If so then your clutch is probably slipping.

baldy110 wrote: Does the engine RPM go up but the bikes does not go faster? If so then your clutch is probably slipping.

No, the speed and RPM stay constant. It almost sounds like the RPMs have hit a ceiling and bounce off of it, up and down. Does that make sense?

Could be plugged main Jets... dirty fuel filter in the fuel selector or even points bounce.

Pics of the bike first. I want to see what kind of carbs you have and the overall condition.
Oh and welcome.
Steve

swest wrote: Pics of the bike first. I want to see what kind of carbs you have and the overall condition.
Oh and welcome.
Steve

I will put up pics soon. The carbs have the pods on them but that is about it.

The PO had rebuilt both carbs and tuned them before passing it to me. As I said, the bike ran like a damn top just last week. Out of nowhere it does this.

I would put money on clutches going out. If it were carb issues it would run like a scolded ape than completely fall on it's face

Lazyman06 wrote: I would put money on clutches going out. If it were carb issues it would run like a scolded ape than completely fall on it's face

I was thinking it might be a clutch issue, and at the same time hoping it wasn't!

The bike starts right up, idles great, and runs great. So I didn't think it'd be a fuel issue, but when it gets to the top end of each gear it pegs out. Are clutch issues big issues? Considering I just got the bike and I ran great that was not issue I thought I would have, but I guess that's the fun of an older bike!

Really depends on the bike. Looking at a micro fiche it doesn't look too challenging if you know how to wrench

What does "pegging" out have to do with clutch slippage?
It sounds like the engine runs out of fuel from the original post.

Yeah, sounds fuel related to me. Might try putting half a bottle of seafoam in the tank.