Hyper 7 Mach 28 Cylinder Head Gaskets

[DPEACE]

Hello, Anyone advise me if a Mach 28 I bought second hand and failed to start might be because there are no cylinder head gaskets fitted.

 

It really is fairly new and should but even the local model shop could not get it to even fire. All compression and other checks on carb/factory settings check out fine with good fuel being used.

 

Would having no rings stop it from firing???

The manuals on line show a 0.1mm and a 0.3mm gasket fitted I think.

 

Any advice appreciated.

 

Thanks, David

[Anthoop]

Yes the head should have two shims...one is aluminum (silver-0.3mm) and the other brass (brass- 0.1mm).

They are often very tight on the head and can be difficult to see...a finger nail or blade should be able to lift them a little.... if they are there be careful not to bend them if trying to remove.

 

Starting issues can be due to many things (really your model shop should have been able to fix or diagnose...).

 

Some questions:-

Can you see fuel flowing to the carb. when you are priming?

Does the plug get wet or the engine flood when you are trying to start?

Have you tried a different plug?

Have you tried warming the engine before attempting to start?

[DPEACE]

Reply,

 

 Hello thanks for the reply.

 

I checked that the shims were not on so will get some from Modelsport and try with starting engine them one of each installed.

 

Fuel flowing fine and even some in carb or down glow plug hole does nothing

[Anthoop]

Usually if an engine has compression then it will fire providing everything else is ok....I can only guess that it would still fire without the shims but as you said they are only a couple of quid so no harm in trying.

 

Got any pictures of the top of the piston and underside of head (combustion chamber)?

[Nitro RC Nerd]

I've run mine without shims no problem.

[DPEACE]

Hello, Well I got the shims and without changing anything (with the carb at factory settings), I could not believe that it started first time! The top of piston and underside of head were really clean as the buggy was reputed to have only had 12-15 tanks through it which on all round condition looked correct. Cant undersatnd why the head  had been taken off and shims taken outy!?!?!!?

 

So, I can only assume that on this particular engine and with the Big Bang 20% fuel the shims did make a difference.

Run it a couple of times now and its really nice idle, runs at correct temp range with great pick up and revs out well.

It will get sold to fund a second/spare Truggy sometime....this time a new one without any hassles.

Thanks for all the advice everyone.

 

David

[Anthoop]

Good stuff....and thanks for the update. 

 

Often people will remove the shims thinking that it will increase the potential of the engine....(I am sure I did this a "few" years ago...shhhh  )

Edited December 10, 2014 by Anthoop

[Nitro RC Nerd]

When I ran mine without its shim...that was not on purpose.;-) Once I forgot to put them back on and once I put them on top of the button head. I normally don't jack with shims unless there is a problem--as you can get yourself in a world of mess if not careful. It's a tough little engine though. Unsure if they are using the same pipe (19229) but that's a horrible pipe. Put an 063 or 063 on it and it's like a new engine!

 

One note...back in the day the manual that came with it stated the stock carb settings were wrong. I had one that said  3.5 HSN / 2.5 LSN, another that said 4.5/2.5, and distributors were stating 6.5 hsn and 3.5 LSN . Luckily I took pictures of it when I first got it and realized it was really flush/flush (as it should be). Mine's been sitting in a box for over a year, but I think I'm going to fire it back up soon. Am happy to roll film on different pipes for anyone considering a new pipe.

Edited December 11, 2014 by Nitro RC Nerd