Sounds like a Subaru and loss of power

Totally hating this bike... bike fix 1 thing, something else doesn't work. Really close to selling it now.

I'm riding home today from work and the bike is going fine no problem. 70 degrees, 35min ride. About half way home while cruising at about 45mph, exhaust sounds different and feels like it's struggling. I stop at a light and she bogs some. Rev while waiting, no problems. Put into gear and start to roll, and she sounds like a Subaru and has a major jack of power. Shift into 2nd, it continues and I pull off the road. Everything looks normal nothing wrong. Little low on gas though, so figure I'd fill it up. Get on road, same thing continues. Fill up, bike runs fine. Filled with mid-grade.

Blocks away from home, it does the same thing again. No power and just sounds like it's struggling. Does it the rest of the way home.

It had done this once before and I shut it off, and then ran fine.

Put about 250 miles on since the carb rebuild and this seems like it's getting worse now.


In neutral she revs fine. ONly once there's a load it does it. Any ideas here? Thanks guys!

Perhaps fuel starvation.

Would test-run with fuel cap ajar (loose and not snapped down) to see whether the symptoms persist.

If the symptoms disappear with the cap ajar, the cap vent is likely malfunctioning for whatever reason.

If the symptoms persist with the cap ajar -- at least the possibility of vent malfunction has been eliminated as a probable cause.

Good Fortune!

That would explain why there was a change when I filled up for gas then. I will actually go out right now and test that out. Will try to get it to do it again and then pop the cap and see what happens. I didn't know these caps are vented.

Of course when I ride, it doesn't do it then. Going on longer ride to the gym in a few so will try then.

As far as the vent on the cap, where is that? Looking at mine, I have the rubber seal and looking under it, I dont see any vents or air passage ways

Forgot to mention, the petcock is just a straight fuel valve, so no diaphrams or anything to fail on. Brand new unit, short fuel lines from tank to carbs.

The vent is in the gas cap. The link below shows how the cap on the KZ650 is set up. I now your cap looks different on top, but it is possible the vent is similar in nature. Ed

kzrider.com/forum/3-carburetor/590974-fuel-starvation#605056

Another possibility is some form of crud inside the tank that's suspended in the fuel. And as the fuel supply diminishes, more crud hovers around and settles onto the petcock tube pick-up screens that protrude up inside the tank. A fresh supply of gasoline may partially flush the screens, which temporarily allows better fuel flow through the screens -- until the fuel gets lower, and the issue reoccurs.

It often helps to flush out the interior of the fuel tank.
Remove tank.
Dump gasoline.
Dispose of properly, and try to keep from blowing up the neighborhood.
Add about 2 quarts of fresh gasoline or common household rubbing alcohol.
Shake the tank to slosh the gasoline or alcohol.
Fast dump the gasoline or alcohol out the filler hole.
Repeat.
Most of any crud inside the tank should now have been flushed away.

May also help to remove the petcock and carefully clean the pick-up screens.

Good Fortune!

When you went through the carbs. Did you remove the Float Needle Seat assy. The Needle Seat has an inlet screen, these can plug up.

I will pull apart the gas cap tomorrow and see what's all going on under there. Thanks for the link!

On the way to and from the gym (about 4 miles each way), it didn't do it at all. I was thinking about these 3 times it did it, and they were all when it was a lot of stop and go driving. Coming home from work its all traffic and traffic lights. When I stopped and filled up, it cured it. The rest of the way it was again all stop and go traffic. Going to/from gym, it was a little bit of highway and a couple lights and was cooler out.

Petcock is brand new (installed last week) and the screens were all clean and flowed great. I thought about the crud in the tank too, but I have a full tank when it did it the second time coming home after filling up. Should flush it though, will probably do next time tank gets low.

I will be taking her to work again tomorrow and see what happens. Will pop open tank if it happens and see what happens then. If that doesn't fix it right away... well I guess I'll limp it home somehow.

Appreciate the help!

Motor Head wrote: When you went through the carbs. Did you remove the Float Needle Seat assy. The Needle Seat has an inlet screen, these can plug up.

When I rebuilt them originally I cleaned it, and then a professional rebuilt them after me so can only assume he did that too.

Open your carb drains into a container you can see in, like a clear glass. Look for debris/ crap. If there is junk there, you might be in for another carb clean. You Have to clean the tank, when you go through the carbs. Do you have an In-line filter?

Well it happened again on the way home from work. Didn't do it there but did it on the same exact strip at the same exact time. Was really weird. This time I felt it coming on before it got to the point. Started feeling uneasy and then started bogging down. PUlled off to the side shut it down and popped the cap and let it sit for 2min. Put it back down.

Further up the road, same thing... pull off to the side, pop the cap but this time kept it open. Ran really well and got further than the 1st time today and the 2nd time, but it still did it again.

I"m emailing the dude that rebuilt the carbs to see what he thinks, maybe he can run through it because he last did them. But looks like I'll drain the tank this weekend and clean it out and check the screens and filter.

Any other ideas besides garbage in tank and now clogged carbs? It seems to only do it when it's warmer out now. This morning it was about 55* or so, this afternoon coming home is about 70. Tank is full again too with new gas, topped it off.

Thanks

Ok so I talked with my guy who had rebuilt the carbs and told him about the situation, and he says it sounds like an ignition problem. Says to check when it happens again, to feel the headers and see if 1/4 or 2/3 are cooler than the other pair.

Only downside of this is that it doesn't happen until it's been running for a while and the headers are burning hot by then. But I will check it out.

But does the ignition sound like something that would cause something like this? I've been looking up about the advancer and how to clean and lubricate it up. Does you think maybe it's sticking? Anything I should know before opening it up?

Also going to check the wiring going to the coils. I haven't had a chance to look at the manual to check what needs to be good as far as voltage but is there anything I should be looking out for? Plugs are new, wires are newer.

Thanks!