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Old 16-08-09, 10:06 PM   #21
colinbryan
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Default Re: 2 stroke running in

thanks guys for all the advice
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Old 16-08-09, 10:39 PM   #22
Bluefish
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Default Re: 2 stroke running in

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Originally Posted by Doinitmyway View Post
Sorta simple really. Air and petrol burn best at 1 part petrol and 14parts air. Engines are mostly set to run just ever so much richer than this. This is because the incoming petrol also helps cool the piston crown.

To make it simple imagine a 150cc single cylinder two stroke engine. To get maximum power AT FULL THROTTLE, every time the cylinder/piston 'sucks' in it will draw in 140cc of air and 10cc of petrol and make nice power and stay at good temp.

If too much air gets in, say 145cc, then there isnt physically room for more petrol than 5cc. All the petrol will burn but not all of the air so fresh air gets into the exhaust (wonder why they're called O2 sensors ). Power will be down a bit and also because there is less petrol to cool piston crown it can overheat and sometimes melt

[if a two stroke runs too rich with oil then that oil will take the place of petrol in the mixture making the mixture leaner still]

If too much petrol gets in, say 15cc, then because only 135cc of air has been drawn in *there is not enough air to burn all the petrol* - this means no fresh air but some petrol will make its way into the exhaust. Power will be down and petrol can be smelt from exhaust.

This is theoretical and other factors do have to be taken into account (air density, temperature, volumetric efficiency etc etc) If you get your head round the fact that the engine size is a limit on the amount of mixture that gets drawn in then it gets easier.

Geek mode off...................................


well that made sence to me, **** i might have learned something
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Old 16-08-09, 11:07 PM   #23
ogden
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Default Re: 2 stroke running in

I did 200 miles on my stroker today. That cost me 40 quid in petrol and 8 quid in oil.

Aren't two-strokes marvellous?
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Old 16-08-09, 11:22 PM   #24
Stu
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Default Re: 2 stroke running in

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Originally Posted by ogden View Post
I did 200 miles on my stroker today. That cost me 40 quid in petrol and 8 quid in oil.

Aren't two-strokes marvellous?
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Old 16-08-09, 11:29 PM   #25
ogden
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Default Re: 2 stroke running in

Peak consumption was Aylesbury - Bicester - Thame - Fox's.

Roughly 65 miles, 13 litres, 22 mpg. Plus oil.

When you have complete and total confidence in your tyres (and BT090s rock mightily), great things can be accomplished.
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Old 17-08-09, 03:41 AM   #26
MattCollins
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Default Re: 2 stroke running in

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Originally Posted by colinbryan View Post
thanks guys for all the advice
It should have been mentioned somewhere (I thought it was) that if it is just the bore that is being rebuilt, then the rest of motor and gearbox is already run in so it doesn't need an extended run-in period. Rings and bores are bedded in the first few miles, so give it a bit (without thrashing it) once properly warmed up (on the road, not at idle) for 20 minutes or so - it needs load to seat the rings properly against the bores... definitely don't coddle the motor. After that ride it normally.

A few links that you might find helpful to avoid a repeat:
http://www.mrfunnel.com/Mr._Funnel/Home.html - get one and use it! Read the first link to find out why
http://www.ultralightnews.com/engine...istonfail1.htm multiple pages
http://www.smellofdeath.com/lloydy/p...diag_guide.htm

Cheers
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