hi guys

my stepdad's bike has been quite rich since hes had it. it has had a FULL rebuild including all gearbox bearings etc but still has this lingering issue that we cant work out. it drinks a litre of 2 stroke pretty easy (under 400 miles). My bike of the same year and setup last's around 700+ miles.

He's getting alot of black oil coming out the exhaust, runs very rich through the rev range. Stock jetting, float height has been set as per manual and it has a 3MB head with 3 wire powervalve, stock front pipe with a DEP rear. the pump operates correctly via the cables and also bob's up and down. the little marks on the pulley line up nice. i dont get it, because these pumps cant really be "adjusted"?

typical really because he wants to sell it soon as he's doing his DAS but obviously cant sell it like this.

Hello Martle, The only 2 things i could suggest are a duff pump (stuck open internally somehow) or there is a slight leak somewhere ?

Be careful though becuase if its running very rich on 2 stroke oil it could lean out the mixture alot and cause a big hole in places you dont want one(piston)

Cheers

Oh yes they can the stroke of the pump is to long re shim it to take the stroke out,bet someone had it appart and didn't put them back in.The alingment marks are to set the rotation the pump,, stroke length determins how much oil gets injected,per stroke. easy fix if you follow the book.

gotcha, nice one guys. i knew it had to be something like that. i will premix it for now till i sort the shimming. wemoto have the shims in stock, i will get a digital gauge on the shim's that are on there now and report back.

Thanks!

You are comparing bikes miles per litre of 2 stroke. Are these the same bikes, ridden the same way on the same roads. I don't think 400 miles a litre is bad. Before you do anything, do the maths. a common ratio of 2 stroke to petrol is 1:33 so for each litre of 2 stroke, the bike should be using around 33 litres of fuel.

If the bike is doing 60MPG, this is around 13 miles per litre (60/4.6). so extrapolating this; 13 (miles per litre) X 33 (33 litres of fuel @ a ratio of 1:33) gives you 429 miles per litre of 2 stroke.

Looks about right to me.

Black smoke sounds like gearbox oil is getting into the mix somehow. The smoke should be white.

Go Have a lie down DT you must be exhausted mate!!

The smoke should be BLUE.

Riding style will make a big difference. If he is chugging around at 3 to 4000 rpm with big throttle trying to use torque it will go through oil and fuel like an Arab.

If he has a lifetime of car driving behing him 7k rpm will sound horrid. Even though thats where the bike wants to be.

The smoke should be BLUE.....

Sorry Jason.

2 stroke exhaust should be "Hint of Lilac" from the Dulux Solo range

Hey its a water pumper. You dont want pure brilliant white either.

True. That would be "hint of antifreeze" from the "I think its fecked" range.