Vintage Dirt Bike Q & A

Hi all,

I have recently bought a 1978 CR125M Elsinore everything there but rough this will be completely rebuilt but rught now just want to satisfy myself that the bike is what I remember!!
bike starts good will tick over nicely it tends to fart and pop a bit as I increase the revs then becomes stable again at about 2500-3000 rpm(I'm guessing the r.p.m.) then revs right through to max very cleanly, however when in gear under load on releasing the clucth tends to want to stall just doesn'nt seem to want to know, give some more revs but just wants to cut out, timing is spot on (according to manual) standard jets, float correct height, needle currently set in the middle position but have been up and down seems to have no effect same thing with the air screw seems rather puzzling. I don't currently have an air filter, that is ordered but I wouldn'nt have thought that is so detrimental to the basic function!! or is it?

cheers for any info

Malcolm

_________________
1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

first, i would have to say that no air filter can definately affect how your bike runs. that could be part of the problem. i would wager that the slow jet is partially blocked. take the float bowl off the carb and get that little guy outta there and clean it. may as well clean the main also. and while you are at it, clean the tank out and affix an inline fuel filter. actually, taking the whole carb off and rebuilding it would be a better option.

be sure to post your results of what it took to fix it.

Hi Jake,

Yea thanks for the info, the filter is ordered. The carb is totaly stripped and currently being chemically cleaned in-line filter is in place and the tank has been thoroughly cleaned out with new feulmix 40 to 1 (40 litres fuel 1 litre oil Castrol 747) However, talking to the mechanic and told him my symptons...............he seems to think that it could possibly be krank seals, classic signs of sucking in air through the seals loss of power under load!! get my carb back wednesday and will rebuild and try again with the filter aswell and hopfully bobs my uncle and off I go!!............. well at least that's plan A!! Plan B being a complete strip and restore.
The carb that I have is probably the original any info as to where I can get jet needles from and the various jets? done a bit of googling but I can only seem to find the newer versions I might have to go for a new one any suggestions?

Cheers

Malcolm

_________________
1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

you are on the right track i think. never rule out a clogged slow jet until you are 100% sure it is clear. some times a single strand of wire(out of a stripped piece of normal wire) is what i use to clean the most stubborn jets. not really supposed to use any kind of metal, but sometimes strands from a broom just dont cut it. the original carb is a kehin, i think some folks have upgraded to a mikuni. i dont see any reason to if you are not actually racing. i wouldnt worry about new parts for the carb just yet either. but what do i know, its not like i am actually looking at the bike.

i hope its not crank seals, thats just gonna keep ya from riding a little longer.

i have a 79 cr125 but i lucked out and got mine in good running condition so i didnt have to trouble shoot quite as much as you. good luck my friend.

Hi Jake,
yea thanks mate I'll keep ya posted as I progress I'll get some before and after pics up shortly

Till then keep ya feet up

Malc

_________________
1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

I agree you should be absolutely sure that all carb parts & orifices are clean & clear. But you just can't beat new brass in a carb.

I would steer clear of any carb rebuild kits as they are known to be of lesser quality than OEM and jet size accuracy is questionable.

OEM jets can be bought here:

http://www.jetsrus.com/

Terry

hey terry, are are for sure right about new brass. i am just too cheap most of the time. that link for carb parts is pretty good. i am sure i will use them at some point.

As for a wire to help clean out jets, I normally strip the wire from inside a twisty from a loaf of bread or trash bags. Wire will go through pilot and main jets and help dislodge gunk in them.