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Post Info TOPIC: Tdc, cam chain new(ish) and cams not level.


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Tdc, cam chain new(ish) and cams not level.
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Hi all, 

My bike starts okay however my cams are both slightly off level when tdc (single mark).

I have recently replaced the cam chain (2000 miles Max) so wasn't too worried.

 

Having rebuilt the bike to a 350 and using a air fuel ratio gauge I'm trying to ensure it's running nice however I'm having a bit of a mare so going back to the basic principle before touching jetting again.

 

I wanted to check my valve clearances however as at the the cams aren't 100% flat I cant take a valid reading.

 

Can any one suggest possible reasons why the cams aren't flat?

 

My initial thoughts

 

1.The cam chain tensioner was initially installed with liquid gasket as I didn't have a spare gasket (was going to be temporary, but forgot to change this). Would 1mm shift in the cam tensioner matter or would it just extend further as it's an auto?

 

2.I haven't doubled up on any gaskets by mistake.

 

3. Highly unlikely but could the yam chain actually of stretched.

 

Something just isn't adding up 

 

 



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Daniel Lee



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As long as the lines are level, the cam lobes will be in the right position regardless of the flywheel, so you can check the clearances ok while we ponder what else is going wrong.

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Hi Dan

I know you are having a bit of a struggle and don't think the gasket/ sealant would have any affect at all, the only way to check the chain would be to have it measured against a new one, but doubt it would have stretched already.

Maybe a visit to TTR towers, so me Bri and Simon could give you a helping hand?

(if the others are ok with that) I know Simon has loads on at the Mo, so may be just me and Bri?

Anyway I am happy to help.

Steve



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Simon - so before when I was rebuilding the engine I couldn't get the cams spot on level AND tdc, so I set up the clearances by rotating the cams individually so that when they were flush they would beclose to clearance spec when tdc However, surely if I then drape the chain over set to tdc and as close to level cams as possible this would mean actual ignition would be either retarded or advanced?  Probably also meaning when firing the valves wouldn't be open the correct amount? 

 

Am I over complicating this? It's an old engine but I just want to be sure as I love the 350 and don't want to risk it!

 

I've been fine doing that with past bikes and other ttrs so I'm happy that I am doing this right :) 

 

Steve - thank you for the offer, much appreciated! I think ill measure the cam chain just for piece of mind then get back to you all:)



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Daniel Lee



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I've had a look at this again as just wanted to check. I used a steel ruler as a flat comparison and sadly I can clearly see the chains stretched a bit already as the cams are not both level.

It is only slightly stretched but if its went that far after 2000miles max I'm worried about the rate of stretching being so quick it could risk the engine in the near future.

 

What worries me is that the bike was very quiet at the start of uk lockdown, very little tapping noise. I started it up yesterday for 5 mins and it was much noisier even when warmed up.

Also just checked the tension of the chain between cams and it was very loose!


Best change it to be safe, hopefully this will help with my poor jetting ability.







-- Edited by dlee22 on Tuesday 26th of May 2020 11:49:58 AM

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Daniel Lee



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i would say that is ok probably a bit of backlash

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Hi Jonny,
The slack inbetween the cams has increased no end compared to February time. The cams remain in the same position when I checked the slack so I think the tension is correct.

It's a shame i don't know how to post the videos as the difference is easy to see

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Daniel Lee

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