Misfire at 5000RPM

[Gerrit]

Hi All, strange problem.

Noticed a dead headlight on my way home after work Wednesday.

Replaced headlight it worked, all seemed fine.

Off to work Thursday morning, the bike starts to misfire at exactly 5000rpm. It idlkes fine, pulls great up to 5000rpm.

Now the carbs was off recently for a cleanup, cleaned filter etc.

I think it is electrical.

Clecked the rectifier this morning, all the way to 5000rpm, I get 15.5v on the multimeter, from the battery.

The I stripped all the plastics, and searched for a loose electrical connection or loose earth, but all seems fine.

Checked the side stand switch, also not the problem.

Went for a spin around the block, after I put it all together, and at 5000rpm the misfire is still there, I did notice though when back in the garage that the headlight seems less bright than usual?

A mate of mine at Honda SA mentioned that it could be the "stator" I checked the values as per the manual at the connecter, and it is .1ohm, within spec.

Nevertheless I opened the clutch cover and pulled it off to reveal the stator, it seems ok, not burned at all, but there is some oil on the stator...Should there be oil on the stator?

Anyway any ideas where else I can search for this mystery 5000rpm misfire.

Many thanks in advance.

Gerrit de la Rey

[IgorVigor]

Sounds like you might have a similar problem to me :S

Mind you, 15.5v seems a little high :S

I havent received a reply in my post yet, but the main suspect for me is fuel tap diaphragm

[Gerrit]

Thanks Igor, yeah I am sure mine is not fuel related.

Also I have a fuel filter filter on each line either side going to the 2 carbs and they are full of oil, plus the bike runs smooth from idle to 5000rpm.

Waiting fir the experts to help me out

Gerrit

[benny hedges]

carbs been off???
slides been out???
diaphragms ???

i'd check them if i was you bud - you mightve nipped one putting it back.

[tony.mon]

Gerrit, does it clear after 5000?
Does it rev out to the redline ok?

[Gerrit]

Hi Tony!

No that is the worrying thing, it will not go past 5000rpm, as the misfire is too severe.

Gerrit

[benny hedges]

in that case you need to pull the cam covers & timing plugs off and check the cam timing is right before you spend money on stuff you dont need.
follow the guide as though you are fitting new ccts.

could be the coils have broken down, ignition advance not working (is that possible now?)
on the fuelling side, i had a similar issue once on my ft where the clip had come off the needle and it had fallen into the tube, blocking it almost completely.
stumped me for a while - coincided with me fitting yoshi cams so i also thought id fkt the timing up as i didnt have a manual. cant really go wrong with a single tho lol!
just thinking at 5k rpm you would be coming off the needle, but usually if it's weak / rich it would just be flat/ lame & not misfire as such???

so id say first off check the cam timing just to be sure, then coils off ebay - but doubt they would both fail at once, then cdi unit.
you have checked the plugs under the tail are secure and not soaked off the jetwasher? maybe pull them off & reconnect?

[Gerrit]

Thanks Benny, I will work thru ur suggestions, only problem is the the GP is on shortly, then SBK, and the the Eng-Germany game...

Damn life is a carnaval here in SA at the moment :)

Gerrit

[benny hedges]

bet it is bud - didnt notice your location til you said...
start with the simple stuff imo, saves time stripping everything off then realising it was just a loose connector
i thought id killed mine after a 160+ blast (ON MY PRIVATE ROAD O/C) but realised it had run low on fuel and coughed a carb off due to me neglecting to do up a rubber in my haste to pwn a gixxer which was roaring up & down the expressway!

then a blocked idle jet on one pot due to me not masking the tank when i sprayed it and a snotter of gongealed paint getting in...

[tony.mon]

I suppose you could check the TPS connector by the carbs, it's on full advance by 5.

Can you leave the voltmeter in place while you rev it? Or is it a steady 15.5 all the way up to 5000?

BTW, oil in the stator area is normal.

Can you borrow a reg/rec from anyone locally to swap over and try?

And as this is what started you off, try removing the fuse to the lights and run the engine up- see if the problem disappears....

[Gerrit]

Thanks Tony, I just did a battery swop, made no difference.

I will work thru ur suggestions, and get back to u thanks.

Gerrit

[Gerrit]

Dunno what else to try.

Carbs are fine, fueling is OK. TPs is fine.

Coils OK, Stator OK, Battery & Rectifier is OK.

Timing is correct.

Maybe it is a terminal issue within the motor ?

Gerrit

[benny hedges]

doubt its terminal - itd sound like a bag of crouton if it was... rumbly through the pegs etc.
i still wonder if either the cdi unit is buggered or something wrong with the advancer??
(behind the clutch)

does it not just want a good caning??? clear its throat?

[Gerrit]

Hi Benny!

Nah I can not get past 5000rpm.

I live 5kms from work and every morning it is a blast to 9000rpm thru the gears, to work and back.

CDI, yikes they cost an arm & a leg at Honda SA, I'll see what the manual says about the advancer, I also read in the manual about the "ignition pulser" I will still check that out.

Bummer is i have to use the car to work now, I hate that , hate trafic, I ride bike summer winter rain or shine

Gerrit

[benny hedges]

you know what i think????

when you had carbs off....
you didnt tighten a main jet proper and it's fell off into the bowl.
5k, needle out of the tube, beugh pft pft berrr eheugh pft....

hava look will you


and have you got vacuum to open the slides???
are you absolutely certain the diaphragms arent fkt, on both carbs ??
if one isnt opening proper you get your symptoms - as though the carbs are ridiculously out of sync...
one pot pulling the other round under compression...