Bike acting sluggish

Hello,

This morning I start up my bike and I noticed the exhaust sounded kinda funny. I also noticed the bike was kind of sluggish and less responsive.

I pull the bike into my shop and look at the carbs, now that I think about it I didn't look inside the passage, but the jets appeared to be spotless, along with everything else. I am using a glass fuel filter, and it looks pretty clean. I had rebuilt these carbs two months ago as well. I do have a small rust seem in my gas tank, but the fuel filter appears to be perfectly clean as I said.

I had noticed when I twisted the throttle that some black smoke shot out the front of the bike (the exhaust was leaking right at the exhaust collar). I had just been using permatex copper silicone in place of an actual gasket. I do have some crush type copper exhaust gaskets now though, I just haven't installed them.

Would an exhaust leak cause a loss in power and kind of chuggish/sluggish engine behavior at low rpms? It would explain why the exhaust sounds kinda funny.

The bike in question is a 1977 KZ650B1

It has pod filters, 117.5 main jets, and 17.5 pilots. I am using an electronic ignition and dyna coils.

My exhaust has 1 and 4 go out through the left pipe, then 2 and 3 out the right pipe.

Perhaps misfiring on one cylinder.

Would install brand new spark plugs (per factory specs), and test run.

Good Fortune!

paulstanely45 wrote:

Would an exhaust leak cause a loss in power and kind of chuggish/sluggish engine behavior at low rpms? It would explain why the exhaust sounds kinda funny.

You bet!

It can also damage the exhaust valves in your engine.

With pod filters, your should have a 1 size increase on your Pilot Jets, and roughly a 4 size increase on the Main Jets, with the needle clips being moved down one notch (raising needle) to make midrange richer.

GL!

You may very well be running on 2 or 3 cylinders... Exhaust will definitely sound funny when you drop some cylinders. if it is 2 of them 2&3 or 1&4 - you could have a coil going out or timing way off for those cylinders. If it is one cylinder or a combo that is not on the same coil - check carbs (choke circuit too!) and also check for vacuum leaks in carb manifolds and exhaust.

I was about 100miles from home on my first long ride yesterday and suddenly my exhaust started sounding weird (deeper?) and when I would get on the throttle not much would happen... after a while it would go back to normal... pretty sure I was dropping cylinders! no fun! (I'll start my own thread to solve that issue )

good luck!

EDIT: if you are on 3 cylinders and a choke circuit is clogged on one of them it will take FOREVER to warm up, one cylinder may not really warm up at all even after taking it off choke. And pulling from a stop will be very difficult... been there done that.

I don't think any of my cylinders are missing or not firing all together. I had forgot a spark plug wire off when initially looking into the issue and it ran rough. Put it back on and it started running good again, I believe all 4 cylinders are running just fine. Ill check for spark tonight.

My coils are brand new, and my timing is bang on (using the dyna electronic ignition)

When installing the copper gaskets, do I need to use any silicon with them?

paulstanely45 wrote:

When installing the copper gaskets, do I need to use any silicon with them?

NO. That copper stuff( imo ) tends to cause more problems than it fixes in exhaust systems. Make sure you clean all the old stuff out too. Otherwise you will have leaks with you new copper gaskets. Do it right the first time.
Pat

Still no luck after replacing the exhaust gaskets.

Im not sure if I am just imagining it, but it kind of sounds like it did when I would leave the choke on. A bit of a deeper sound than it usually has.

I bought some seafom and put that into the gas tank, let it run for a bit, but havent done much riding.

Any other suggestions?

Once again, I took apart the carbs, but like an idiot I didnt look in the passages, I just looked at the jets. I will be going down a jet size though pretty soon, so Ill be sure to make sure that all the passages are clear.

The big problem I notice is that it seems kinda sluggish when I am in first and getting going (i.e. letting the clutch out to get moving).

i know this may sound crazy but what is your chain tension like and also how often do you lube it and check for tight spots or worn teeth on the sprockets. i have seen a bad chain cause symptoms sort of like your describing.

My chain is a wee bit loose, and I lube every 500km. I probably did go a bit over this time though. That wouldnt explain the exhaust though would it?

no that wouldn't explain the exhaust, hard to tell without actually hearing it anyway. the chain thing can explain the sluggish acceleration but definitly not the exhaust.

I have a muffler on each side of the bike.

cylinders 1 and 4 route out to the muffler on the right side of the bike (the side my right leg would be on if I were sitting on it). Cylinders 2 and 3 obviously run out the the other side.

The muffler that 2 and 3 run to was puffing out white smoke this morning, and yesterday. After I ran the bike for a bit it appears to stop. I noticed the other day when investigating, that cylinder 2's spark plug looked pretty black and wet, oily if you will. Where the pipes for 2 and 3 meet the muffler seemed kinda wet and oily too.

Im getting the impression I have some worn rings or a valve problem. Any recommendations to help narrow down the issue?

before i checked compression or anything else smell your oil it sounds to me like you may have a float valve problem.if you can smell gas in your oil that would comfirm it. also check you oil level if it has gone up thats a good indication ,as well from the way you described the the color of the smoke it sounds like a overfueling problem to me. if it was burning oil it would be blue smoke. so i would not be zeroing in on compression related problems.if the oil level is higher than normal remember this oil doesn't grow so the extra would have to come from somewhere. leaking petcocks and float valve assemblies will cause that to happen.