Engine noise help!!!!!

[baab84]

96 Kat 750 with 50,000 miles. I have asked the question before about the so called sewing machine noise and I have the cam tensioner spring. I am still having the noise problem. Bike runs great and no noise at ilde but speeds up till about 4000 rpm and stays constant after that. All valves have been adjusted and visually inspected. there is a worn cam lobe on #3 cyl, could this be the cause?? ANY suggestions would be appreciated! Another question about the cams. On the 88-96 kats why am I finding two different cams, a 1 lobe per cyl and a 2 lobe per cyl. any help??

[hightop]

I guess it could be that your chain has stretched past the parameters which could be taken up by the adjuster, it's hard to say. The different cams are because early 600's had a single lobe with a forked rocker which did both valves, and later have a shim and bucket arraingement where each valve has it's own lobe and bucket. Your's should be a bucket head. I don't think a worn lobe would cause the noise.

[The CyberPoet]

Kats are somewhat noisier than other motorcycles in general due to the lack of water-cooling (water jackets normally act as an additional sound-deadening layer in the engine), but the sewing machine sound is usually indicative of a cam-chain tension issue. When you installed the new cam tension spring, did you poke a bic pen barrel through the hole for the tensioner button, to clear any oil-sludge build-up at that spot? Not a bad precaution; built-up sludge can render the spring ineffective by blocking movement of the tensioner button -- a good oil and regular service intervals will help prevent such sludge build-up at the tensioner button.

I suspect the worn cam lobe may play heavily into the noise. There was a manufacturing defect in the hardening process of certain pre-98 years' cams that resulted in their pitting under adverse conditions. If the pitting is directly over the valve stem or tappet-activation area, and is more than half of the acceptable valve adjustment range (i.e. - if the intake range is .004 to .006", the pitting should never be more than .001"), I would suggest replacing the cams specifically, or better yet, replacing the entire head with the screw-adjuster heads from a 98+ model (which are not susceptible to the same pitting under normal circumstances -- but I'm not sure what changes might be required for the cam chain to accommodate such a conversion, having never had a pre-98 myself).

As noted above by hightop, the valve-activation system varied for the 600's with the same variations of the nut-adjuster vs. shims from what I understand. 98+ and all 750's had nut-adjuster valve systems that included a single lobe activating a tappet that depressed both valves simultaneously. Note that when adjusting common-tappet activated valves, you should shim the valve you are not adjusting at that moment to ensure there is no see-saw action going on at the tappet that might throw your adjustment values off (e.g. - if adjusting the left exhaust valve for cylinder number three on an engine that uses a tappet to activate both valves to .008", place a .008" feeler gauge under the right exhaust valve before adjusting the left one).

Cheers,
=-= The CyberPoet

______________________
CyberPoet's KR Specials
Suzuki Stratosphere - 6 Cylinders, the new Katana?
The Best Motorcycle Metal Billet Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.

[DreKat]

I had the same problem. I broke a valve. The Exoust valve head broke off and wanted to go out the intake valve....eather way it ost me $800 to get the new valve replace and I had the get the engine machine due to the fact that the piston was pounding on the valve.

If this is your problem you will save yourself a few bucks if you drop the engine yourself!