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Timing a timing chain on a Smart car (Read 2855 times)
backinthegame
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Timing a timing chain on a Smart car
11.11.10 at 20:07:19
 
Evening guys,

I dare say this sort of thing has been discussed many a time...

I've bought two Smart cars with knackered engines. I've done one and made an effort to time it properly, but got it wrong and I think it done a valve - it makes a very expensive sound if it is started - I had it all back out and discovered i had got the timing a tooth out, gambled on the re being no permanent damage, but was wrong, there is.

So, for no particularly good reason, I've started on the next one. I am at the stage now of timing it up, but I can't seem to get the timing spot on. I've been playing around moving the chain 'backwards and forwards' from one tooth to the other, and no matter how much I convince myself i've got it right, after spinning it over by hand a few times and checking it out, the timing marks are not lining up spot on - it always end up a third-to-a-half of a tooth out.

As far as i'm aware there is nothing especially difficult about timing these engines up, but boy I'm making an issue out of it.

Has anyone got any advice they can give me?  Embarrassed
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shoysty
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Re: Timing a timing chain on a Smart car
Reply #1 - 12.11.10 at 07:55:52
 
have a look on the how to guides here ,www.fq101.co.uk ; very good site
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backinthegame
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Re: Timing a timing chain on a Smart car
Reply #2 - 12.11.10 at 08:53:02
 
shoysty wrote on 12.11.10 at 07:55:52:
have a look on the how to guides here ,www.fq101.co.uk  very good site


Thanks, yeah that's the one I'm currently being guided by. Amazing piece of work.

The Oracle down the pub last night has probably pinpointed the problem, the chain will have stretched. That's not to say the chain has worn and the sprockets are certainly not worn, but chains do stretch.

So it seems that I can't get the timing bang on due to this slight problem, and the two choices I have depending on which tooth I go for is to be slightly advanced or quite-a-bit-more retarded. Of course on a modern engine it is both valve timing and ignition that would be affected.

If I go advanced that would mean the engine would run hotter, if I go retarded such a tiny engine m ight suffer a significant power loss. Whilst advanced is the most risky, it is also the lesser degree of 'out' if you know what I mean. Think I'll go and check it again and put the pully on to get an idea of just how much I'm taking about.

(On the Smart engine you can check the timing without the crank pulley-with-notch because when the timing is set properly the wooderuff key is spot on at TDC.)  Smiley
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wheelnut
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Re: Timing a timing chain on a Smart car
Reply #3 - 13.11.10 at 17:58:37
 
You should count the number of teeth on the cam wheel and divide the result into 360. That will give an indication of how much the timing is out in terms of degrees. The error on the crankshaft will be half* the figure of the cam and most of us will be able to relate better to such a figure.

If the problem is due to chain stretch then the logical thing is to put the chain on the "retarded" tooth because that's where it would have been anyway. However I see in Shoysty's link that these engines are prone to break a plastic chain guide and that could also cause slackness in the chain. I presume you have checked that?

*Edit: just thinking about that again, maybe I should have said "twice the figure"?
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wheelnut: Every man's future is decided in the ladies' loo.
 
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mac 54
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Re: Timing a timing chain on a Smart car
Reply #4 - 13.11.10 at 20:15:40
 
that chain is knackered
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Anna Rack
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Re: Timing a timing chain on a Smart car
Reply #5 - 13.11.10 at 20:22:11
 
Could it be that after you've turned the engine, the tensioner is going slack causing the timing to move slightly?
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