GPX750 won't rev

[Barclay]

Austreetfighter.com sell MX kits, they're basically tow mounts with M8 bolts, you drill into the headstock and bolt them on, then attach the bars to this, this may have to be the way to go. The last owner seems to have fabricated the bars, so he could lower the front end.

Thanks for all the help and suggestions!

[Neka79]

Austreetfighter.com sell MX kits, they're basically tow mounts with M8 bolts, you drill into the headstock and bolt them on, then attach the bars to this, this may have to be the way to go. The last owner seems to have fabricated the bars, so he could lower the front end.

Thanks for all the help and suggestions!

yea mate, or u can go to ur local dirty store and buy a Reikon Fatbar kit which has the conversion bar risers in it, for abt $200 (ive just been looking for bars myself)..also it gives u the option to go 7/8 or Fat bars (thicker and stronger)....

yea u do need to drill ur top clamp tho...its not that hard..if greeny was about id tell ya to pm him (he just did his cbr and loves his fighters)

[Barclay]

I found a cheaper alternative yesterday. I stole some bars and clamps from a BMW R100, drilled the headstock for one hole, and made a backing plate for the other. The clutch line fits but the brake line will need lengthening at some stage (have loosened the brake divider)

Made an amazing difference to the bike, much more comfortable to ride now you're not leaning over the bars.

Adjusted the needles one more notch, i think that's about as far as I can go without changing jets. Runs pretty good

[Phil]

Has anyone mentioned shorted sparkies or leads, had the same issue once with the motor not reving past half way.Only found the shorted lead when I was testing each plug for spark and zapped the shit out of me self .

And yes the $25M GPX is back on the road with new enlarged valves off a ZX10 (not the new one but the original) along with a further modified head to match. They are stainless steel competition valves, lets hope they last longer than the stock GPX ones. So I be out terrorising all and sundry this sunday down nasho.
Also had new jets and needles installed and the beast goes SOOOOOOOOOOO much better.

[MadKaw]

Has anyone mentioned shorted sparkies or leads, had the same issue once with the motor not reving past half way.Only found the shorted lead when I was testing each plug for spark and zapped the shit out of me self .

And yes the $25M GPX is back on the road with new enlarged valves off a ZX10 (not the new one but the original) along with a further modified head to match. They are stainless steel competition valves, lets hope they last longer than the stock GPX ones. So I be out terrorising all and sundry this sunday down nasho.
Also had new jets and needles installed and the beast goes SOOOOOOOOOOO much better.

Did someone say Dyno Day..??

[mike-s]

haha, i think i heard an echo somewhere.....

Might have to start thinking about it seriously, and lets hope the whole air fuel ratio thing is sorted out now for the mighty highly modified zxtenneysevenfifty.

[Errol]

Hey Barclay,
In my experience I have found CV carbs to be very sensitive to vacumn changes.
On the ZRX, putting a K&N filter in the original airbox was fine. BUT just removing the (snorkel) inlet tube to the airbox mean't the bike died badly @ around 5500rpm. Playing with the Dyno-jet kit, & up ten jet sizes cured the problem .
I would suggest completely removing the airbox AND filter would play havoc with them. You will need to go up about 12 main jet sizes I suspect. Maybe up 2 pilot jets would not hurt, assuming you have pods fitted when tuning AND riding it. This would be relative to previous well tuned set-up, including a full airbox & filter.
Alternatively re-fit the airbox AND filter & re-evaluate .


Any exhaust re-burn valves/circuits in the head/tappet cover need to be blocked off also if fitted.

[Phil]

Has anyone mentioned shorted sparkies or leads, had the same issue once with the motor not reving past half way.Only found the shorted lead when I was testing each plug for spark and zapped the shit out of me self .

And yes the $25M GPX is back on the road with new enlarged valves off a ZX10 (not the new one but the original) along with a further modified head to match. They are stainless steel competition valves, lets hope they last longer than the stock GPX ones. So I be out terrorising all and sundry this sunday down nasho.
Also had new jets and needles installed and the beast goes SOOOOOOOOOOO much better.

in case you hadnt figured it out that was tim using my signon, his sign in wont work for some reason, dave can you check that out. and also appears to have appreciated somewhat

i'll run the zrx up if there is a another dyno day, AND i wanna see matt chan's zrx there, he showed me some pics of it the other day and it looks senfarkinsational - me like - LOTS

[Neka79]

re- brake lines...

as u have lifted things by a few inches the lines will b a touch short..

stu at aus street fighters does HEL braided lines with a 6inch overlength for exactly this reason...
admittedly he isnt quite as cheap as supperbike supply at the mo, but u can get overlength

[Shifty]

An old thread, but I'll confirm the airbox will have been the problem.

I was in a hurry and didn't bother puttinjg the airbox lid back on my GPX600R and the farker wouldn't go above 5000rpm with any kind of throttle opening. Replaced the lid and voila she was a rocketship. Well, 80-odd horsepower of rocketship anyway!

[Smitty]

An old thread, but I'll confirm the airbox will have been the problem.

I was in a hurry and didn't bother puttinjg the airbox lid back on my GPX600R and the farker wouldn't go above 5000rpm with any kind of throttle opening. Replaced the lid and voila she was a rocketship. Well, 80-odd horsepower of rocketship anyway!

hmmm
not long after i got it, I had no airbox on my GeePeeX7fiddy..and the filter was a piece of filter foam
taped across the carb inlets

never had a problem with revs either...coz it pulled 12000rpm in 6th down the chute at the Island

[Neka79]

never had a problem with revs either...coz it pulled 12000rpm in 6th down the chute at the Island

on the way to those "1.27's" ??

[Johnnie5]

At full throttle I don't think the needles are doing much at all, it's just main jets and a lot of air going past them. So you'd think that they're either putting too much fuel in or not enough...but then reading back over earlier posts, it's the same with different sets of carbies, so you wouldn't think it would be the settings on them...

Ahh bugger, I don't know, I'm out of my depth again. These things are so much easier when you can see what's going on.

yep correct at WOT the mai9ns come into play

yes 2 sets of carbs, who says either of them are right

check the plugs, if they are black then would be looking at 2 rich

check the mixture screws as well