jerky overrun

[prime]

i absolutly love my mk3 since i bought it a few weeks ago but one thing has been bothering me and thats the snatchy/jerky overrun, or when im trying to use half throttle the bike splutters quite a bit. When i bought the bike the first thing i noticed was the size of the rear sprocket, and upon further investigation realised its a 54 tooth sprocket on the rear with the standard 14 on the front. Would this gearing cause the snatchy feeling?.

thanks

paul

[helisupp]

Check airscrew setting first, and for any potential air leaks.

On the overrun it does not matter what gear or gearing you have as you are off throttle.

[fallenmikethebike]

i absolutly love my mk3 since i bought it a few weeks ago but one thing has been bothering me and thats the snatchy/jerky overrun, or when im trying to use half throttle the bike splutters quite a bit. When i bought the bike the first thing i noticed was the size of the rear sprocket, and upon further investigation realised its a 54 tooth sprocket on the rear with the standard 14 on the front. Would this gearing cause the snatchy feeling?.

thanks

paul

14/ 42 is standard, 13/45 is mostly run, I like 14/45, on my MK3, this I feel gives a good compromise between fuel economy, and performance. IMO.
Check plug for colour, and other checks as mentioned.
Mike

[twistednuts]

Check airscrew setting first, and for any potential air leaks.

On the overrun it does not matter what gear or gearing you have as you are off throttle.

Are you sure?

[knackeredMk1]

First - Clean out the carb. Look at the jets you have and record the sizes. Main and pilot.

Compare these with standard and note any changes from standard for the bike. eg exhausts............

Try to rejet more accurately and adjust air screw.

Second - Almost all CRMs have a snatchy/jerky feeling off the throttle when slowing down. This is due to imperfect jetting changing the needle position and the airscrew can make some difference but you probably won't be able to erase it completely. Raising the gearing will help but you will loose some low speed acceleration.

The bike you have is nearly 20 years old and it didn't run perfectly under the described conditions when new.

[prime]

thanks for the help guys i will try all of these suggestions much appreciated

[fishtail]

actually the jetting might be a red herring? depends how u define sputtering? I was havin issues in the low mid range of the throttle and actually it was cos me power valve wasnt aligned correctly ( must have been the numbskull who put the new TRX piston in )

checking PV alignment does seem easier than 'playing' with the jetting?

[prime]

fishtail wrote:
> actually the jetting might be a red herring? depends how u define sputtering?
> I was havin issues in the low mid range of the throttle and actually it was cos
> me power valve wasnt aligned correctly ( must have been the numbskull who put
> the new TRX piston in )
>
> checking PV alignment does seem easier than 'playing' with the jetting?

The spluttering is around the mid range, its more like the bike hesitates for a second then I wind on
The throttle and it just picks up and pulls nice and cleanly. When I get chance I will check the pv alignment and
Try the other checks

[prime]

hi all

ive finally got around to stripping my carb down for a good clean in order to try and reduce the stuttering at 1/4 throttle opening and also the horse kicking on the over run. I did all the checks that you guys suggested and there are no air leaks at all the pv marks are spot on and the pv opens and closes as it should, its just had a new twin air filter and a new plug. I stripped the carb down and found the main jet is a 152 and pilot is a 45 and the bike is running a full dep system. This was my first time stripping a carb so i got my mate to double check the carb and he said its clean as a whistle inside as are the jets and the jet needle is in the middle postion. just before we put the carb back together does anybody know what the float height should be set at? its on a mk3

cheers all

[knackeredMk1]

http://www.crm250.com/specs.asp

[prime]

thanks knackered

[prime]

Another question im about to put the carb back on the bike on my own and just wanted to check which way the slide goes back into the carb?

[fallenmikethebike]

There is a locating groove on the slide that must marry up with the notch inside the carb body.
Failure to marry these two together will leave the slide hanging half raised, and ready for run away RPM if you start it like this.
When re-assembled, pull the throttle, it should be smooth action, with no grounching, and when you let go of the twist grip, you should be able to hear the slide body ground out in the carb, and feel it as well with your hand.
Mike

[prime]

Cheers mike thats great

[prime]

Well I got the bike back together last night and used it for work the morning and its still the same lurching back and forward while coasting and revs still staying up for a few seconds at traffic lights the dropping down to a normal idle. The settings for the carb are all stock except for a 152 main jet the mixture screw is 1 1/4 turns out and needle in middle is there anything else I could try to reduce the problem?