Melbourne ZXR expert

Hi All,

Does anyone know of an expert in the ZXR250 that lives in Melbourne?

Too many issues to resolve and painstakingly slow to find info. Always easier to talk to someone.

Any help would be appreciated.

Cheers

 

It's for the drag bike.

A bit of background.

I bought the bike as a non-runner. The engine had a valve that had folded back on itself. My "Head" guy said the valves are titanium and there's nothing he can do to repair a damaged valve on this bike. We bought another engine from a local importer who said the was out of a wreck and a quick compression test came up trumps. My mechanic mate put the carbs and all the other bits onto the new engine and then stripped as much weight out of the bike as possible. My mechanic took the magneto out as well as all the wiring. The starter motor is still in the bike. We run a battery in the bike and to start it you just turn the kill switch to ON and hit the "make bike go now" button. We didn't touch the cooling system or the carbs/airbox. Engine seemed to rev okay in the garage and we tried it with and without an exhaust. Exhaust is aftermarket megacycle system, but we'll run without exhaust for the drags. We went to Broadford for a shake down before attacking the quarter mile. Bike ran very badly. Would not rev over 13,000 in first and even less as you went up the gears. The bike's idle was also playing up...it would start off okay and then jump to 4,000 once the bike was revved. My mechanic slowly got on top of most of these issues, although he never figured out why the bike wasn't revving properly. By the end of the day, he'd managed to get the bike to rev to 14,500 before we packed it on the trailer. My mechanic has since found that the bike's main jets were incorrectly installed. normally they are 122;125;125;122, but ours were 125;122;122;125. He seemed to feel this is what was causing the bike not to rev out properly. He has since changed the jets to 125;128;128;125 and we hope to run the bike this weekend to see if the problem has been fixed. personally, I don't think so, but hope to be proven wrong. When I bought the second engine I was told it was out of a ZXR250, but upon closer inspection we have discovered the block was manufactured in 1993. We are running the carbs, headers and CDI from the original ZX2R bike on this engine.

My questions/queries are as follows.

1. The ZXR 250/4 produced 45HP in the pre-1993 configuration, but dropped to 39HP after 1993. What did Kawasaki do to reduce the HP? If you're not sure, please don't answer this question. We need to know exactly what was changed.

2. I've read on this forum people taking about using a de-restricted CDI for the ZXR. What does this mean and where do I get one?

3. Does running iridium plugs make any power difference?

4. Will running the engine without a muffler cause it not to rev to its redline?

5. Running bigger main jets and no exhaust...should I remove the standard airbox?

6. I've also read about people running hotter cams and also boring these engines out. Does anyone know anything about this?

7. Has anyone ever made an EFI system for the ZXR engine?

I'm sure I'll think of other things to ask the group, but these are the most concerning ATM.

Thanks

 

Hi Phil,

Definitely haven't thrown the towel in. Just after information as per the 7 points on my post.

Thanks

 

I hear you Grey. The whole exercise is pretty pointless without a baseline. Not my doing unfortunately.

Having said that, I trust the mechanic and he is doing or has completed doing most of the tasks you mentioned as we speak (except for valve clearances). I expect the bike will go much better on Sunday. Maybe I will wait until then to post again.

Cheers

 

Hey Gang,

Back from a good day at Heathcote Park Raceway. Bike still refusing to rev out properly, but mechanic has made great progress. He tried a few different things today and by the end of the day we were running mid-fifteens (15.42 best) with 85+mph top ends (88mph best). Now, we all all know these bikes can do a lot better, but considering the reduced revs (won't rev past 15,500 without breaking down); 45 tooth rear sprocket and fat bastard jockey (100kg+) I think those numbers aren't too bad. Stinking hot there today too.

We're chipping away at it and hopeful of getting it running true soon. While the bike won't rev past 15.5k it now does this in every gear. Before, it would just die as you went up the gears...third gear would not rev past 8k and going to forth was run ending. At least now I can change up before it starts to break down. My mechanic has made changes to the fuel system, but I'm wondering if the CDI might benefit from a change. I will probably swap the CDI from my green bike onto this one and see what affect that has on the revving issue.

Thanks again for all your ideas and feedback. It is genuinely appreciated. I will update this thread as we move forward.

Cheers

 

Phil (&Chris),

That's exactly what I was thinking...that the CDI might be the problem. When it hits 15,500-16,000rpm it's almost like the electronics are acting as a rev limiter. The bike runs beautifully right up to that magic number and then nothing. We wanted to add an extra plate to the clutch so Saturday I pulled the clutch out of the original engine and the plates were burnt to buggery. I expect that the engine that was in the bike when I bought it may not be the original engine that came with the bike. The frame had scratches that looked like the engine had been pulled out at some stage. Given the PO didn't mention any of this when I purchased the bike, it stands to reason that there may be a plenty of changes from standard. Also, my mechanic pulled all the wiring out of the bike (saved about 2kg of weight) so I'm not sure what standard looks like. I will have a look when I get home tonight.

Chris, do you have a diagram or image of the 2 different CDI contections? All I have is an exploded view of the A electrics and that just shows the CDI box from the back end and no connectors etc.

I think the CDI is looking more and more like the likely culprit.

Cheers

 

Thanks Chris.

Let me see what's on it tonight and I'll get back to you.

Does anyone know exactly what the A and C models supposed to rev to?