4 stroke engine doing strange things

karlp · Mar 24, 2008

I have a 4 stroke engine that I am rebuilding, however the valve timing marks are a little hazzy.

When I turn it over the carbs blow out instead of sucking in and the exhaust sucks in instead of blowing out - ie it it just as if the carbs and exhaust should be connected the other way round.

I am assuming the valve timing may be out by 180 degrees - any suggestions.

thanks

karl

Gas'd Off · Mar 24, 2008

Daft question but are you sure your turning the motor over in the right direction

karlp · Mar 24, 2008

I had thought about that - but the motor is electric start so is turned when pressing the button.

karl

(RIP) Proff · Mar 24, 2008

Giz a clue, what engine is it ??
I've got loads of miniature engines plus I've a lot of single cylinder tech manuals..

Remember golden rule is Crank goes round twice to camshafts once, so it could be 90 degrees out not 180

karlp · Mar 24, 2008

It is a kawasaki z650 engine.

It does spin the correct way on the starter.

I do think the timing is out but wanted to check other peoples opinion first.

thanks

karl

(RIP) Kaister · Mar 24, 2008

NO 1 PISTON AT tdc - use a pencil in the plughole and check the timing marks on the crank.

inlet cam faces outwards at 90 deg and exhaust is pointing 180 deg away.

use the nearest timing marks on the sprockets.

If this doesn't work-you'll need a degree disc and first principles - or a clymer manual

T900 · Mar 25, 2008

as you were doing a rebuild, make sure you didnt get inlet and exhaust cams mixed up, also double check your valve clearance to be sure they are not tight.
ALWAYS turn the engine over by hand with the plugs removed before turning over on the starter, then you will be sure that the pistons are not going to clip the valves :augie

D6 · Mar 25, 2008

cam timing, check u aint 180 out and that u use the CORRECT MARKINGS on the cams, there are different ones, difrent models

(RIP) ugg · Mar 25, 2008

wen i was doin my gpz i made novice mistake wen setting cams, they wer 180 out , i forgot that its two turns of crank to one revelution to the camshaft followers :blast

D6 · Mar 25, 2008

ugg said:
wen i was doin my gpz i made novice mistake wen setting cams, they wer 90 out , i forgot that its two turns of crank to one revelution to the camshaft followers

thats the one!ur learnin :thumb2

180 out

(RIP) ugg · Mar 25, 2008

sempi, cohi :bow

180

karlp · Mar 25, 2008

thanks for the repliers

The inlet and exhaust cams are not mixed up - there is no way that can be done as the exhaust has an rpm driver wheel on it.

I did check theat the engine would turn by hand and all was ok.

valve clearances have been checked and double checked.

I will check that it is not out by one cycle as that is my first thought. - probably on week end then report back.

thanks all

karl

4 stroke engine doing strange things

karlp

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Gas'd Off

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karlp

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(RIP) Proff

25 Mar 1949 - 10 Nov 2016

karlp

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(RIP) Kaister

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T900

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D6

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(RIP) ugg

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karlp

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