ZXR power delivery issue .... bike shop thinks I'm making it up!

Hi guys


Hope all's cool in 250 world. I've got this issue with my 1989 ZXR250 and wondered if anyone's encountered it before or suspects what the issue is?


Basically it's a power delivery problem. The shop replaced some cracked/perished vacuum tubes that feed fuel into the carbs (this was after I sent it to them with the problem it occasionally would stall when hot and be impossible to re-start), and now I have issues with getting revs/power.


Even after I've run it to be hot enough that it idles fine without any choke, I can rev it and it struggles to get over 2-4000 rpm (normally it would rev over 10k no problem). The other day, I couldn't get enough revs to get out of my carpark ramp (stalled when I applied more throttle). When I eventually got it outside (been running about 10 mins by that point), I couldn't get enough revs to get over about 30kph and had serious issues getting across intersections.


After running for about 20 mins, that issue seems to go away in first gear and I can get normal revs there, but in 2nd/3rd gear I still have a delayed/jerky response to applying throttle. It's like the engine's starved for fuel.


The shop is trying to tell me replacing the tubes has prevented the engine sucking unfiltered air and therefore has taken performance back to the original state. I can accept that, but I don't accept the way it's behaving is normal - it shouldn't be struggling to achieve any acceleration at all when it's warm and this just seems straight up dangerous - I have no power to achieve even normal riding around town. I'm wondering if there's a blockage or something isn't connected right.


Any ideas? Help much appreciated!


Charlotte

 

Thanks for that - yes, it makes sense to check those things. Because I'm in NZ I have no tools. I would have hoped that since I just paid the shop a big whack of money they'd have checked those things, but who knows.

 

Kiffsta - thanks for that awesomely detailed reply I will try to get a hold of some tools and give those things a go. The NLA parts are always a concern - let's hope it's not one of those, but if so will give your fix a try also.
Cheers,
charlotte

 

Yes it was - this is a brand new problem that I never had before it went to the shop. I think this is the reason they are trying to tell me that it's just the new vacuum lines having changed performance - I think they're trying not to hear that it's actually a *problem* not just altered performance. I know the difference between less response on a throttle and *none*.
My husband picked it up from the shop and they had had it running for a long time before he got on it (it's also not his regular ride). I don't know honestly if it's something that's happened between the pick-up and home, but they're the last people to have it apart and they've given it back to me in what I consider a non-ridable state.
I'm very appreciative of all the responses - I'd love to have a go at fixing it but being in Auckland means I have no tools or place to work on it really - and I kinda feel that having paid the shop money they should fix the bloody problem that I think they might have created (or at least, not picked up before they sent it back). They had it for a whole week.

 

A bit of update ....


Did another run this morning to more clearly describe the problem for the shop. The problem was still exactly as described in the first post. So I rang them and pinned them down on whether they thought it was normal or not. They acknowledged not but suggested I try changing tank (had been running off reserve as this was their recommendation in these bikes) ....


I then switched the bike over to the main tank and took it out again. Initially it didn't seem to make any difference - still getting loss of power or jerky power in 2nd/3rd gear particularly around 6000 rpm. But then, after a few laps around the block and a run down the waterfront, this problem seemed to clear up. By the time I got back, there was no longer a discernable issue. Bike Had probably been running, I'd guess, about 20-30 mins at this stage (and was started hot from my earlier ride).


So, the shop now suggested the fuel tap itself could be the issue ... and I did wonder with the tap being further "upstream" from the engine, and have cool fuel going through it, if it might take a longer time to warm up (if it's more a problem when cold), hence the problem taking a while to go away.


Still not sure though - my course of action now is to restart the bike cold on the current (main) tank position and see if the same problem happens. Then, back to the shop.

 

Yeah thanks for that. We actually have a ZZR too (1994 model), though thankfully no problems like this what that yet.


The shop were supposed to have cleaned the tank and all the lines when they did the last work, so if it is muck it must be something they missed or something new. Will let you know the outcome.