Post all the small engines stuff here. Cox, Wen-Mac, Testors, Spitzy, Wasp, Holland Hornet, Atwood, Aurora, Gilbert, etc.
Moderators: Frank Klenk, SteveM
by crashnburns » Tue Jun 26, 2012 11:40 am
I have a Norvel .061 that I think is new but on cranking it becomes very hard or stiff at the top of the pistion. I can not see any thing looking in sleve or back plate that could cause this ? Any ideas will be appreacited.
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crashnburns
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by SteveM » Tue Jun 26, 2012 12:24 pm
The Norvel motors are known for having a pronounced 'pinch' at top dead center (TDC) and this is common on several other motors as well. The sleeves are built with a slight taper towards TDC to improve the piston to cylinder seal. These motors did need lots of fuel durng break-in and to ease the stiffness at TDC some owners would use a heat gun on the head so as to expand the head and reduce the stiffness. Perhaps reducing the compression a bit by installing an additional head gasket might help. I do not have any first hand experience with these motors so I cannot offer much more.
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SteveM
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by crashnburns » Tue Jun 26, 2012 2:31 pm
That would explain it as the motor was new but no paper work. It must need that break in process.Thanks for your reply.
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crashnburns
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by Frank Klenk » Tue Jun 26, 2012 3:59 pm
Steve is absolutely correct. Cox Tee Dee's are the same, taperd cylinder.
The best thing to do is as soon as you start the engine get it to full throttle to get it hot so the cylinder expands right away. You want to avoid a cool running engine as this will scuff the bore at the top. Dub Jett and Nelson engines are the same and they recommend getting the engine up to temp right away with full throttle. This is how I broke my Dubb Jett in and it runs perfect every time.
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Frank Klenk
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by crashnburns » Tue Jun 26, 2012 6:16 pm
Thanks Frank, I will give it a go.
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crashnburns
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