Page 1 of 2

Revving problem

Posted: Sun Feb 26, 2017 2:55 pm
by Chris sweets
Good afternoon fellas
Bought a bike which I now know was from a dodgy dealer, started having issues with it after about a month
The issue is the reviving, when the bike is started it idles fine, when your on the throttle the revs can jump all over the place even when you are holding the throttle steady, there is some popping from the exhaust when this happens
Anyone got any ideas or know of any common faults this could be?
I have searched on the internet and I'm going to start it up in the dark tonight and check from any sparking/arching, I'm also going to spray a mistake over the engine when it's on file to see if the revs change if it's taking in water from somewhere
Any help is appreciated

Re: Revving problem

Posted: Sun Feb 26, 2017 3:32 pm
by tastethefloor
have u check the plugs?
is the fuel "fresh"?
valve timing is correct?
is the bike already fittd with manual cct?
do u know if the pevious owner did some mods inside the carbs?
good luck

Re: Revving problem

Posted: Sun Feb 26, 2017 4:08 pm
by VTR Phoenix
Could be carb air leak, check carb to engine boots are tight and clips done up and carbs are seated properly.

Re: Revving problem

Posted: Sun Feb 26, 2017 4:09 pm
by Chris sweets
I have no knowledge at all of bike mechanics and only slight basic knowledge of car mechanic
the fuel is fresh and is BP
No idea what a cct is
And I thought the valve timing couldn't be adjusted
As far as I know there has been no mods to the carbs but it has got road legal scorpion cans on

Re: Revving problem

Posted: Sun Feb 26, 2017 4:23 pm
by tastethefloor
popping from the exhaust is related to too much fuel unburnt in one cylinder.
start with a plugs and coils check

or take it to a mechanic

Re: Revving problem

Posted: Sun Feb 26, 2017 4:28 pm
by Chris sweets
Is it easy to check the coils, how will I know if it's them?
There is a definite popping from the exhaust 90% of the time that the revs change

Re: Revving problem

Posted: Sun Feb 26, 2017 4:32 pm
by tastethefloor
I will check the plugs first, maybe I change them..

the valve timing could not be adjusted but could be wrong. a teeth more or less in one sproket in both exhaust or intake cam can lead to yours ymptoms

Re: Revving problem

Posted: Sun Feb 26, 2017 4:38 pm
by MacV2
Chris sweets wrote:Is it easy to check the coils, how will I know if it's them?
There is a definite popping from the exhaust 90% of the time that the revs change
That is more likely to be an air leak in the exhaust system somewhere...Check all the joints are fully clamped up tight...The std clamps rust very easily so one could have failed...

Let us know where you live & someone local may be willing to help you.

Re: Revving problem

Posted: Sun Feb 26, 2017 4:39 pm
by Chris sweets
Changing the plugs first it is then

Re: Revving problem

Posted: Sun Feb 26, 2017 8:01 pm
by lloydie
Check the vacuum pipe .

Re: Revving problem

Posted: Mon Feb 27, 2017 7:44 am
by Chris sweets
I live just by leominster in Herefordshire

Re: Revving problem

Posted: Mon Feb 27, 2017 10:06 am
by AMCQ46
Chris sweets wrote:I live just by leominster in Herefordshire
not to far from me, so if you are still struggling in May bring it to my workshop day and we can look at it and swap parts

Re: Revving problem

Posted: Wed Mar 01, 2017 8:29 pm
by 8541Hawk
As I stated in your other thread, check the diaphragm in the petcock for leaks. :thumbup:

Re: Revving problem

Posted: Wed Mar 01, 2017 9:07 pm
by VTR Phoenix
8541Hawk wrote:As I stated in your other thread, check the diaphragm in the petcock for leaks. :thumbup:
Easiest way to check this is remove both fuel pipes from under the tank, leave the fuel tap switched on, if fuel continues to come out of the petcock then the diaphragm has a hole in it.

Re: Revving problem

Posted: Sat Mar 25, 2017 5:30 pm
by Chris sweets
Amcq where abouts are you? It's starting to get decent weather now so I'm dying to get out on it