Author Topic: Won't rev past 6k rpm under load! (Read 10062 times)

Robbie8666 · « **on:** 24 September 2015, 03:17:39 pm »

as title, bike been in workshop for nearly 3 months now & mechanic no further forward!!
HELP!!
when not in gear bike revs all the way to red line
in gear the bike pulls & revs smoothly up to 6k in all gears but won't go past that
mechanic bought Yamaha's manual direct from Yamaha has checked all voltages etc
he has changed ecu
spark plugs
HT leads
stripped & cleaned fuel system pump filter
stripped & cleaned carbs
balanced carbs with electronic tool and compared against each other
checked coils and all with in tolerance
check clutch for slippage
has checked side stand switch as that was suggested by someone

a) has anyone had this & fixed it?
b) any other ideas where to try next!

I have got to the stage where I said i'd sell it but he reckons with the problem unfixed I'd only get £450 so not going down that route!!
missed a lovely Fazer thou so decided to try & fix this one then when I find the right replacement keep this as a 2nd bike / one for Mrs use

any ideas? getting pee'd off as missed summer again due to not having my own bike!!so 2013 missed summer 2014 rode 2015 missed summer!!

joebloggs · « **Reply #1 on:** 24 September 2015, 04:00:14 pm »

Have you checked the compression?

bandit · « **Reply #2 on:** 24 September 2015, 04:58:52 pm »

Check all the vacuum pipes from under tank to carbs also check the rubber caps on the inlet manifold rubbers for splits or disconnection.

darrsi · « **Reply #3 on:** 24 September 2015, 06:35:34 pm »

Dunno if this is any help?

http://www.therevcounter.co.uk/threads/21097-Engine-won-t-rev-over-6000-rpm-First-thoughts

joebloggs · « **Reply #4 on:** 24 September 2015, 08:13:13 pm »

Quote from: darrsi on 24 September 2015, 06:35:34 pm

Dunno if this is any help?

http://www.therevcounter.co.uk/threads/21097-Engine-won-t-rev-over-6000-rpm-First-thoughts

The ZX6 has ram air intakes, and the problem was air pressure difference between intake and float bowls. My ZX9R had exactly the same issue when I picked it up, the mechanic had forgot to reconnect them during the service and it only effected the RPM at speed when the ram air starts working

Jules-C · « **Reply #5 on:** 25 September 2015, 06:53:45 am »

When was the air filter last changed? That's about the revs it gives problems, it can look OK but still be clogged enough to upset the carbs at 6k revs

joebloggs · « **Reply #6 on:** 25 September 2015, 10:33:54 am »

Over fueling...Choke or float heights?

BBROWN1664 · « **Reply #7 on:** 25 September 2015, 11:29:47 am »

When your riding it, does it accelerate fine to 6K then stop dead at 6K or does it taper off and then maybe creep up a little by little to eventually arrive at 6K?

Restrictor kit fitted??

Robbie8666 · « **Reply #8 on:** 25 September 2015, 01:07:09 pm »

Quote from: joebloggs on 25 September 2015, 10:33:54 am

Over fueling...Choke or float heights?

yeah just checked those this week
yeah air filters checked & cleaned
it accelerates smooth up to 6k then stops dead wont creep past that point,
also when riding and pull clutch in it will rev to 8-9k but as soon as clutch dropped back in revs drop straight back to 6k
he's now looking down the exhaust to see if any internal corrosion blocking pipes

no not a restricted bike, was returning to Portsmouth from Nottingham when fault developed. had ridden up there great. next day riding back joined M40 @ J15 Warwick off A46, went to overtake a camper and splut chough no power!! (well restricted!) had to limp home @ 60mph plus went through a tankfull by Services @ Oxford where I'd gone up from Portsmouth to Nottm on a tank then refilled at start of journey back!

BBROWN1664 · « **Reply #9 on:** 25 September 2015, 01:11:52 pm »

if it happened during a journey I would look at the airbox/intakes and the exhaust to check for anything blocking it. That said, it would struggle up above 6K regardless of engine load. It certainly wouldn't stop dead it 6K having pulled well to that point.
Using lots more fuel is also a clue.

Check the cam chain hasn't jumped a tooth.

Robbie8666 · « **Reply #10 on:** 25 September 2015, 01:29:04 pm »

thanks for all the advice thus far folks

when just chatting to mechanic bout what had been suggested on here he dropped into conversation that he has a very clean tidy SV1000s in that's for sale ( he doesn't sell but people can sell out of there, if that makes sense0
on a 55 plate 13k miles & new tyres 500 miles ago for £2750 so hoping to get an afternoon off work next week to take that for a test hehe

His Dudeness · « **Reply #11 on:** 26 September 2015, 11:33:08 am »

I'd get a set of carbs off ebay and stick them in. Maybe there's wear in there that's not clearly visible. If it doesn't work just stick the carbs back on ebay.

gryphongryphon · « **Reply #12 on:** 02 October 2015, 08:14:58 pm »

Mine used to stutter twas the coil.

Robbie8666 · « **Reply #13 on:** 05 October 2015, 07:49:28 am »

he's checking the float heights this week,

apart from my bike been off the road it not affecting me as mate has let me use his Gixxer when I needed it.
it's just frustrating can't get mine sorted. but hey ho whilst its in with him its not outside in the weather!

Ian-man · « **Reply #14 on:** 05 October 2015, 08:48:02 pm »

I had this sort of symptom and it was a partially blocked air intake. Have you tried running it with no filter just to see if there is a difference.

Robbie8666 · « **Reply #15 on:** 06 October 2015, 08:23:14 am »

yeah that was an early fix we tried, also tried running it with rev counter disconnected, pulling clutch in whilst riding it...
got us baffled!

but please keep suggestions coming in,
oh have changed carbs they didn't make any difference so rules that out

joebloggs · « **Reply #16 on:** 06 October 2015, 09:49:55 am »

Compression check?

His Dudeness · « **Reply #17 on:** 06 October 2015, 10:42:28 am »

Dodgy fuel pump? I just had some weird issue due to a dodgy fuel pump. Try bypassing it totally and see if it gets past 6k

crickleymal · « **Reply #18 on:** 06 October 2015, 11:02:44 am »

There's got to be some clue in it revving to 6k then no further under load but being fine off load. Also in it being fine on the journey down then suddenly going wrong on the way home.

I can recall having something vaguely similar on my first post test bike (Kwak Z250). I had trouble tuning it up then one day found a sweet spot and it was great. Overtook a lorry and I felt the power suddenly go and it was back to doing no more than 70. I never did get to the bottom of that but it was either one of the carb diaphragms causing problems or something to do with the ignition timing (twin points).

As your carbs have been changed it's not that. Have you checked the compression? Camchain? Ignition timing?

stevie-g1968 · « **Reply #19 on:** 06 October 2015, 06:49:08 pm »

What exhaust do you have on your bike? Is it clear, check the baffle has not collapsed or something like that. Seems you have checked the inlet side of things, so it could be being restricted on the outlet side of things.

Robbie8666 · « **Reply #20 on:** 06 October 2015, 09:45:59 pm »

Quote from: stevie-g1968 on 06 October 2015, 06:49:08 pm

What exhaust do you have on your bike? Is it clear, check the baffle has not collapsed or something like that. Seems you have checked the inlet side of things, so it could be being restricted on the outlet side of things.

yeah tried that last week took baffles out & also followed pipes up to ensure no blockages

but thanks

pressure off now as bought 2nd bike today so goona sorn bike whilst its in workshop!

joebloggs · « **Reply #21 on:** 07 October 2015, 08:57:31 am »

Will it rev past 6 in the lower gear's?

Robbie8666 · « **Reply #22 on:** 07 October 2015, 07:27:06 pm »

no Joe, it wont

joebloggs · « **Reply #23 on:** 07 October 2015, 07:38:25 pm »

Anyway of checking if the ignition is going full retard at 6k