ZXR750 rebuild #3

[JimZXR]

Had my first run out today, only a quick run around the doors (23km) but enough to notice it was in desperate need for more air in the tyres and probably a tune up as it almost dies if you ride it below 2500rpm! Above that it sings but thinking it may need a CCT doing due to some noises coming from the motor under load.

Service the motor with some 5100 this weekend to see if that helps.

Tyres, pads, change brake fluid, change out the screen (cracked), tank protector, etc all to come but for now enjoying it being there ready to ride!

Not the best photo but happy that its somewhere other than my garage!

[JimZXR]

So I've now changed the oil and filter and I'm still getting a slight ticking sound coming from the motor.
Its not an obtrusive knocking sound but to me its still noticeable.
Can anyone tell me what a CCT needing to be done sounds like?

[BrettZZR]

Exhaust leaks around the header often sound very 'mechanical'. Try running your hands around in there before it gets too hot.

(-8

[SC00BS]

Hi Jim,
Thanks for all the pics of your bike. Hope you get those little bugs ironed out.
Cheers
Scott

[tomithy]

She's looking good Jim!

Very sorry to hear about the issues you had at the beginning. None of those things ever happened to me (she always started up and no jammed fuel caps ever, I swear!).

As an aside, the QA throttle was from a B model 636 from memory. The switch block was a bit slippy on the bar but by that stage she was only ever seeing the track so I didn't pay it too much attention.

More than happy to help out in any way possible. Shoot me a PM with any Q's and I will respond once our timezones re-align

[JimZXR]

Thanks for the intel and offer Tim, may take you up that!
Current issues are around a misfire but may figure it out over the weekend

[JimZXR]

So after checking through the usual suspects and still having issues with what sounds like a misfire I decided to give the bike a good fang down the freeway and try getting it up through the revs and o my surprise it pulls really nicely with no hint of a misfire that I could hear or feel.

After another look over I've noticed the clean air system has been botched up to take it away without installing block plates by connecting the two opposing hoses together; could this be the source of my "misfire" sound?

I'm going to buy a new set of exhaust seals this coming week and will be making some "smog block" plates from plate aluminium then see if the noise clears after fitting all of that!

Anyone had any experience of this? And how much of the under airbox stuff can I remove and have the bike still run nicely?

[greenman43]

You can take all the emissions shit off, just make sure you plug the airbox on the left and have the right side feeding to the carb breather pipe (big black plastic tube across the top).

Cheers,
Brian

[JimZXR]

But would an exhaust leak from the Kleen air system cause a burbling misfire?

[JimZXR]

Still waiting on my smog block plates so thought I'd try to track down the ticking sound; I think it's coming from the fuel pump!
Really strong clicking/ticking sound on revs so thinking I'm needing a new pump?

While out riding I filled the tank and turned the fuel stop back to ON and less than a K down the road the motor died! That'll be a knackered fuel valve then!

It also still has the burbling misfire!

So the list of jobs to do is growing steadily:

- Change exhaust gaskets
- install smog block plates
- change headstock bearings
- check compression
- check plugs/spark
- check fuel pump operation
- potentially install new clutch

Does it ever end?!?

[JimZXR]

After a play with the pilot screw yesterday I got the bike running much better but still not great at low revs.

Had to hook up a remote fuel tank to run it but worked well once I'd got it mounted.

Worked out the creaking in the head stock was incorrectly placed bolts rather than bearings so that was a good find!

Fitted my new smog block plates and removed all of the redundant air hoses too!

After a big ride out last night I'm in definite need of a new clutch so might as well tick if a few if my maintenance list while the clutch is out!

Coming along nicely though I think.

[Kwakked Up]

Still waiting on my smog block plates so thought I'd try to track down the ticking sound; I think it's coming from the fuel pump!
Really strong clicking/ticking sound on revs so thinking I'm needing a new pump?

While out riding I filled the tank and turned the fuel stop back to ON and less than a K down the road the motor died! That'll be a knackered fuel valve then!

It also still has the burbling misfire!

So the list of jobs to do is growing steadily:

- Change exhaust gaskets
- install smog block plates
- change headstock bearings
- check compression
- check plugs/spark
- check fuel pump operation
- potentially install new clutch

Does it ever end?!?

You know that when this is finished you would only find another project, it's an addiction

[JimZXR]

Today I had to do an engine change as the clutch back torque spring has snapped off 2 fingers and one is missing so I decided to do the swap and take some time rebuilding the original motor.
7 hours later and it's a belter again!
Looking forward to some Winter K's next weekend!
The other project bike may have sold to a mate too so all is well in the world again!

[willrcr15]

Hi Jim,
Re the mis fire issue, check that the needles are on the correct grooves.
The GSXR we just got going had a bad misfire issue & we gave up on it & Jamie at Sportscycles at Gateshead found it, we had one needle out of the 4 higher than the rest & that was enough to do it. I was surprised, I was sure it was an electrical misfire. (116hp at the rear wheel on his dyno)
The other thing to check is that one of the carbies aren't flooding a little bit either ariund the inlet valve seat or around the inlet insert, that's something else weve had trouble with on another 4 cylinder bike, we fixed it up with a carby rebuild with Viton rubbers. Turns out it was just the insert rubbers that were leaking not the needle & seat.
I'm jealous of your bikes fairings, mines still sporting grey undercoat, can't decide what scheme to do. I would love to keep it original but the stickers aren't available at all. Let me know if you come across a hoard of fairings, I'd love a set.
The Factory Pro needle & jet kit I fitted along with the pilot jets work beautiful if you want to spend a few hundred more on her.

[JimZXR]

Turns out it's an oil leak Mitch!

Either rings or valve oil seals I think! Can't say for sure as the motor can out before I had chance to do a compression test so I'll have to check it by measurements.