New to the exup scene and need some learned yzf 750 advice

The Sradiator · Post by **The Sradiator** » Fri Sep 26, 2008 12:47 pm

My recently acquired yzf 750 is making a noise that i suspect could be rod knock?

It comes and goes though and is akin to the noise flat slide carbs make when their slides rattle or even detonation sounding.

I have bogged the bike in 4th gear at under 3000 rpms and there is no noise.
Its most noticeable when blipping the throttle in neutral around 2500-3000 rpms.

I am told this is indicative of the exup valve clatter but wanted to ask those in the know!

There is no noise while idling at all.

While i know that internet diagnosing is difficult, any help/advice from long term yzf exup equipped owners would be greatly appreciated!

Thank you in advance for any/all assistance!

Ebolavictim · Post by **Ebolavictim** » Fri Sep 26, 2008 2:06 pm

hi welcome to the fold.

There is a degree of clatter from the exup valve, have you tried inspecting it, if its only when you blip the throttle and at no other time I'm sure this is probably what it is.

how does the bike run through the rev range from the off.

John

The Sradiator · Post by **The Sradiator** » Fri Sep 26, 2008 4:41 pm

It doesn't happen at idle and is most pronounced when blipping the throttle standing still.
I wont say i never hear it when riding but bogging/loading the engine produces none such noise.
I was told by the friend of an fzr 1000's owner who heard mine that his friends emitted the very same noise but im not convinced.
I appreciate the input though.
Bike runs fine from idle on up!

djalbin · Post by **djalbin** » Sat Sep 27, 2008 11:23 pm

Noise in neutral when blipping the throttle between 2500-3000 rpms?
Sounds like slides rattle or even detonation sounding?

Some ideas for the rattle sound ...
It could be the cam chain tensioner is wearing out.
It could be the EXUP valve bushings are loose/worn and rattling.
Also check that all your engine mounting bolts are tight and torqued to spec.
It could be the clutch basket or clutch plates are loose, warped, worn.
It could be an oil supply problem to top-end of the engine. (oil level, oil weight/viscosity, oil supply line).

Some ideas for the detonation sound ...
It could be valve clearance adjustment is needed. Check the service interval against your bike's mileage and see if it's time to check/adjust the valve clearance. I assume the YZF750 service interval is the same as the FZR1000 (26K miles).
It could be fuel quality/octane level
It could be the wrong spark plugs
It could be carbon buildup in the cylinder heads

If it was internal engine parts (e.g. valve spring, piston pins, connecting rod, etc ...) I would expect to hear them through the entire RPM range and get worse/louder as the RPMs increased or the load on the engine increased.

You didn't mention anything about poor performance at low or high RPM range. So it's just noise without affecting performance?

ExupElvis · Post by **ExupElvis** » Sun Sep 28, 2008 11:51 am

djalbin wrote:It could be the clutch basket or clutch plates are loose, warped, worn.

The clutch baskets will make that noise when they are coming apart.
Check it when you get the chance, and go a bit further than just pulling the cover and looking at the outer clutch plate splines - get the basket out, clean it up, and check for cracking from any the 3 rivets out to the outside edge.
If it is cracked on the hub part of the basket you won't be able to see it with the rest of the clutch assembly in there.
I put up a pic of that somewhere here, If I can find it I'll put in the link.
(edit) Here it is -

[/img]

The Sradiator · Post by **The Sradiator** » Mon Sep 29, 2008 10:38 am

The overall performance of the bike is fine.
I don't believe its clutch related. usually when you pull the clutch lever in, a rattling basket will stop rattling! (In my experiences)
At 18,000 miles i guess things are starting to wear.
The noise is faint and almost imperceptible. Did this bike have an aftermarket exhaust system on it, i doubt this noise could/would be heard.
It's not motor mount or hardware noise, of this i am sure.
Having not been the original owner i can say much about it's previous history or how it was used or abused.
Since it is a premier sport bike i'll just ASSume it was not only used for church on Sundays!
The exup cover is off the exhaust and i don't know if that shields/insulates any exup noises from the naked or even the well dressed ear?
I tried the old screwdriver to the ear method with the only results being a headache! Thanx for the imput so-far and PLEASE keep idea coming as i'll address each one and rule them out as i go along.
Thanx Again for the learned words!
Bestest regards...The Sradiator

PS...To clarify something i said earlier...The knocking sound is akin to the sound of detonation. It's not detonation from what i can ASScertain just sounds similar to it.

The Sradiator · Post by **The Sradiator** » Mon Sep 29, 2008 11:06 am

ONE OTHER ISSUE: I have noticed that if i use the chain adjuster markings, that the rear wheel seems to be out of alignment. The markings appear to be 1/2-1 mark off?
I measured from the edge of the tire to the edges of the swing arm in the same place on each side. When i get the numbers equal, the chain adjuster marks are off by almost 1 line.
I have always heard NOT to use the lines as gospel but 1 mark seems excessive!
Is the swing arm symmetrical so that the measurement can be taken from tire bead or rims edge to each side of the swing arm with certain accuracy?
I have the left block facing "FWD" as marked on the block.
I am not nearly the newbie as these posts might imply, just new to the YZF 750 is all.
Thanx again for your patience/input here!

Post by **FZRDude** » Mon Sep 29, 2008 11:13 am

I have always measued with calipers, from the adj block to the front of the ajdustment area on the swingarm.

The Sradiator · Post by **The Sradiator** » Mon Sep 29, 2008 11:22 am

And...when i do that the marks are off but the wheel is centered!
I actually went one BETTER and went from the front of the swing arm where the adjuster bolts are threaded to the inside of the axle on each side.
This eliminates the blocks should there machining be off, which i believe they are!

Post by **FZRDude** » Mon Sep 29, 2008 11:51 am

The Sradiator wrote:And...when i do that the marks are off but the wheel is centered!
I actually went one BETTER and went from the front of the swing arm where the adjuster bolts are threaded to the inside of the axle on each side.This eliminates the blocks should there machining be off, which i believe they are!

That was how I was trying to explain. And yeah, the marks are off.....