Engine shutters when accelerating

So I hae a 76 kz750. Its a great twin ad a daily rider, but i notice when Im at a constant hiway speed, and give it a little more gas I hear a wierd noise like a loose chain rubbing metal, and I feel the engine shutter. I thought it might be out of sync carbs, cause I've never been able to do it with the vacum gauges. The engine noise is pretty loud after a long ride too. Any thoughts or suggestions would be great.

"bump"

I have a 750 twin.

There are three chains:

1) camshaft chain: is adjustable via the adjuster on the front of the engine (between the exhaust pipe outlets).

2) Internal drive chain: can't be adjusted, but sometimes will get loose and noisy in very old engines that have had a hard life.

3) Wheel drive chain. Needs constant attention and adjustment and will make all kinds of noise if too loose. Look at the swing arm and see if there are signs of the chain banging on it.

If you don't have a factory manual, you should get one.

EDIT TO ADD: One more chain, the internal engine balancer is chain drive. Not user adjustable.

Man, I got nothing for you. My top end made noise and I'm pretty sure it was the top cam chain idler. I won't know for a while since I just got my engine together and the bike is in pieces.

KZCool wrote:

So I hae a 76 kz750. Its a great twin ad a daily rider, but i notice when Im at a constant hiway speed, and give it a little more gas I hear a wierd noise like a loose chain rubbing metal, and I feel the engine shutter. I thought it might be out of sync carbs, cause I've never been able to do it with the vacum gauges. The engine noise is pretty loud after a long ride too. Any thoughts or suggestions would be great.

Here's my 2 cents.

If you look down at your chain while this is going on I think you see your chain is wildly flapping sideways during this acceleration at highway speed. Just don't run off the road while looking.. heh. If you have a riding partner get them to watch your chain for you instead. It could be bouncing off the swing arm, the spacer on the back engine mounting bolt, even the edge of your motor casing, or wheel rim, etc. You'll want to correct this.

I've always attributed this chain destruction to the amount of low end torque these motors produce, they tend to actually stretch the chain links open, rather than stretching the chain lengthways. I've had more than one chain that you could hold up sideways and have a half moon... chuckle.

So check and adjust your drive chain and it may go away for a while, but it won't be long returning. You'll have to do more periodic chain adjustments than someone on an inline 4 would have to.

Long ago someone suggested a chain tensioner on the bottom run, which is probably a good idea, but I never got around to it as I acquired a belt drive model years ago.

As far as engine noise increasing on a long run goes. These twins have an extremely noisy top end, the cam noise increases as fuel level in the tank drops and the tank begins to act as a echo chamber, increasing the noise until you fill back up. Check your cam chain tension and adjust if necessary, (don't over tighten) but these motors also use a stationary guide in the cam cover which contributes to the noise.

You'll get used to the noise after while and learn to listen for strange noises instead.. chuckle.

Ive had the bike for a while, and I just replaced the chain. tightened it corectly and everythihng, the teeth on the final drive gear was worn. like the teeth were bent back a bit. and seemed to catch the chain a bit here and there when i spun the tire. Any thoughts about replacing it. it didnt catch bad or anything, but i feel like it has stretched the chain prematurly as it now has more slack than before.

If the chain was worn enough to need replacement, then the sprockets most likely need to be replaced as well. Putting a new chain on old sprockets will certainly shorten the life of the chain. The chain can not fit correclty onto the sprockets.

+1 on the chain and sprockets.
Unless you broke down somewhere and you had to replace 1 of the three to get down the rad, always replace the chain and sprockets as a set, always.
It might be different for racers who are constantly changing gearing for a track, but for your street bike get a good quality set of sealed chain and sprockets.

KZCool wrote:

Ive had the bike for a while, and I just replaced the chain. tightened it corectly and everythihng, the teeth on the final drive gear was worn. like the teeth were bent back a bit. and seemed to catch the chain a bit here and there when i spun the tire. Any thoughts about replacing it. it didnt catch bad or anything, but i feel like it has stretched the chain prematurly as it now has more slack than before.

Personally, I only purchase high quality, heat treated sprockets. I strictly avoid anything made of soft metals. A good set of sprockets with a properly maintained chain wear little, if any, and will outlive several chains. 99% of damage/wear to sprockets is poor/lazy chain maintenance.

I've ridden for over 30 years without ever loosing a chain, but then very few of us actually carry chain lube with us, or would do an adjustment far from home, lol.

However at the first sign of wear I would replace them, and what you describe is to me severe wear. You have likely already damaged the chain beyond redemption.

I'd run right out and get a new set of sprockets and chain like suggested. It is your life we're talking about here, and chains like to crawl damaged sprockets... rear wheel lockups aren't very much fun according to my friends horror filled faces.. chuckle, you get the picture. :ohmy:

YOu guys are right.its definitely not safe. just got my house tax reurn back. can you say shopping spree!! lol Dont suppose anybody whould know here to find a good quality set of sprockets? Do you think it could also be that my valve clearance is messed up so when I give it some more gas on of the valves doesn't seat right?

www.z1enterprises.com

yeah, i went there and got a 32 tooth for my rear, and a 17 for the front. that should add some power ; ). does anyone think i should get a new chain as well, or is the one i have on it now salvageable?