help, possible fueling problem on overrun

[lloydspencer]

I have recently purchased a MK2 CRM. I ride a VFR750 and Aprilia RS250. I have decided to start doing some green laning and was wondering whether it is usual for this bike to be jerkey on the over run as none of my other bikes are like this. When I let off the throttle it seems to be quite juddery and seems like its firing every now and then. Any suggestions would be greatly received. Thanks

[eddie666]

mine is the same, every thing is set up right, they just want to be on the go all the time, i think its some thing to do with the power valve, when the reves are let off the valve will shut and the back presure will build up then push it open like a dump valve then it will close a bit then build up again then so on, untill you open the throtle then the electronic unit opertate the cables to open it at high reves, then its smooth and power full,

thats what i think that happens,

high reves are operated by the elec unit but engine pull back ( no throtle ) is just mechanical flap with springs on the power valve,

if you have a race exhaust that will alter the back pressure also ,

make sure every thing is set up right, oil feed ajusted right / plug corect / air filter clean /carb air leaks / exhaust leaks / fuel mix set right, gear box oil / ect,

i know what you mean, its just the way they are , not like four strokes or none power valve two strokes,

use hi octain fuel , and good two stroke oil, silkolene comp 2 , then you will never get plug fouling and may help with the engine pull back ( off the throtle )

[dietcoke]

Hi, I have the same problem with mine, see this thread

viewtopic.php?f=6&t=5925

So far I havnt been able to fix it, so tend to agree with eddie666.

I wonder if there is a solution tho

[fallenmikethebike]

mine is the same, every thing is set up right, they just want to be on the go all the time, i think its some thing to do with the power valve, when the reves are let off the valve will shut and the back presure will build up then push it open like a dump valve then it will close a bit then build up again then so on, untill you open the throtle then the electronic unit opertate the cables to open it at high reves, then its smooth and power full,

thats what i think that happens,

high reves are operated by the elec unit but engine pull back ( no throtle ) is just mechanical flap with springs on the power valve,

if you have a race exhaust that will alter the back pressure also ,

make sure every thing is set up right, oil feed ajusted right / plug corect / air filter clean /carb air leaks / exhaust leaks / fuel mix set right, gear box oil / ect,

i know what you mean, its just the way they are , not like four strokes or none power valve two strokes,

use hi octain fuel , and good two stroke oil, silkolene comp 2 , then you will never get plug fouling and may help with the engine pull back ( off the throtle )

Yes +1, another good post from Eddie.
Mike

[capt]

Hello,
My Mk2 does the same! but ticks over fine,it has a newly rebuilt engine,I took the bike back into the 2 stroke guro for an inspection.
"quote!" the bike is old and not like modern 2 strokes - we will look at the jetting opptions @ 400 miles - could be carb wear but it did look ok when we cleaned and inspected it - the changed gearing and the 17 inch wheels will make it more apparant - The aftermarket reeds and dep system could also play a role but we dont think so,I am sort off getting the feeling MK2 are a bit like this and off road you would not even notice.

Anyways ,I am booked in this weekend to get the jets changed this may help they stated!

The other tips were high octane fuel --- Rock oil semi sythetic.

I must say if it cannot be fixed I will be gutted -- in traffic is horrable

[eddie666]

in the end its a motocross bike with a charging system, it was built to go as fast as it can, off road they are a top cult classic two stroke compered to the moden bikes of today, in the hands of a top rider off road they can still give the moden bike a good run for there money,

the only fault with the bikes is that we do not use them for what they were intended for ( racing off road ) and we try to make them more road going and exspect them to ride like road bikes,

thats like trying to take a tiger for a walk on a lead, you could do it, but it wouldent be happy for long.

i have my bike as a smile factor toy for blasting about on for an hour or so when ever i can, but if i had to go further than 10 miles to work every day on a bike it would not be on a crm250,

use them hard and fast and safe, then have a four stroke for transport to work or long journeys,

[voodookid37]

quote,
i have my bike as a smile factor toy for blasting about on for an hour or so when ever i can, but if i had to go further than 10 miles to work every day on a bike it would not be on a crm250,

use them hard and fast and safe, then have a four stroke for transport to work or long journeys,


agrees totally.............exactly the way i do it........even in winter.lol

[fallenmikethebike]

The only way I have found is to go for bigger/taller gearing, this allows the engine to be pulling all/most of the time.
However, as is the way of things, you lose out on the, get up and go bit, your choice.
Mike