Pit Bike Club

Rickwales · 27-04-2019, 12:35 PM

It's a job to know if someone hasn't fitted a subframe off a different bike. You need to take it apart and put the seat roughly where it should go and work out what's wrong with the subframe that's there. The seat should follow the lines of the plastic and it should all line up properly. If the plug is black than you are running too rich anyway

jtwales · 27-04-2019, 12:52 PM

Ok thanks I'll take a look hopefully later today.

I think I'm going to order the new carb anyway and then start again. As I mentioned I'm fairly certain it's leaking from the bowl/float area at the very least. Gasket kit is half price of replacement carb

Rickwales · 27-04-2019, 04:32 PM

You may need to re jet the new carb to suit. If you are buying a direct replacement then I would clean out the jets you have and put them straight in the new carb

jtwales · 27-04-2019, 06:06 PM

So I redid the valves again and it fired up and was rideable so rather than fiddle more I went for a blast . Managed quite a few laps , and managed to restart after numerous stalls. However luckily at the top of my field I stalled again and could not get the thing to start. Short push back to my yard and pulled the plug. Black as soot again and I little moist from petrol. I did t have time after that butnim pulling the carb to check it over before I order the new one.

Rickwales · 27-04-2019, 09:17 PM

How many turns is the mixture screw on. Also what notch is the needle on. Depending what Cobb you have you may have an air screw or a fuel screwdepending if the mixture screw is it before or after the throttle slide. You need to lean the mixture probably by half a turn just try it

jtwales · 28-04-2019, 08:23 PM

IV not had the carb off yet to check the needle setting (I can't do it in place I think?). It's a molkt carb, looks like the 26

The air screw I have set to 1.5 turns out from softly seated - to clarify when a 'turn' is specified it is meant as a full 360 degree turn right?

I fiddled with a few settings of that screw and it doesn't seem to make that much difference so I guess next step is checking that notch for the jet? I think I read setting it 2 from the bottom is the default setting?

jtwales · 28-04-2019, 08:23 PM

Thanks for the help by the way !

Rickwales · 29-04-2019, 12:30 AM

If you adjust the mixture screw buy a whole turn and then do a proper plug chop you will see what difference it makes to the plug as it may not make a lot of difference to the performance. What you need to realise is the fuel/ air mixture that you're looking for is actually a quantifiable percentage. You are looking for a air to fuel ratio of between 15 to 1 and 18 to 1. So basically all engines need the fuel and air mixture to be between these figures to run properly. Less than 15 to 1 will run rich and above 18 to 1 will run lean. Once you have the mixture set correctly then the needle position will affect how the engine accelerates. If the needle let's too much fuel in too soon it will flood the engine before the revs pickup enough to burn the extra fuel or if the needle doesn't let enough fuel in it will run lean before revs increase. When you're at full throttle the needle has virtually no bearing on the ribs because at this point it is the main jet itself that is controlling the fuel flow. I hopeThis explanation will help you understand what you're aiming for.