Derby decomp assembly

So yea max Johnson did me up so sweet mods on a derby metrakit head for

My hobbit Athena. I got ahold of a derby decomp set courtesy of the great and amazing Benji. So now can someone'help me as to exactly what goes what in assembling the decomp linkage(jbot please chime in As I know how important a functional decomp is to you)

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Re: Derby decomp assembly

nice cup.

Re: Derby decomp assembly

He isn't it. I hope you are referring to the combustion chamber and not something on the table that is in a pic.

This much looks right as in the first pic.

The second pic looks to somehow be on the right track?? Obviously there is some kind of clip on the end of the decomp that is missing.

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Re: Derby decomp assembly

Here is the decomp sort of attached as per the piston port manual I found in the wiki. I wonder if this hardware is not the right length for this particular head.

It appears that the decomp valve should line up with the top hole in the bracket and then secured with a Circlip. Maybe I should drill a hole above the existing one so the valve can exit. Anybody know what I am talking about. Ed aren't you a derby guy?

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Re: Derby decomp assembly

Or dah! The Circlip goes on the top of the spring and the flat part of the part pushes it down and yea it's all correct!

Re: Derby decomp assembly

you need to compress the spring and spacer so the e-clip or something like that i would have to look at a decomp again. i run no decompression cylinder heads, cause going pull start is like buying hookers, way easy :)

Re: Derby decomp assembly

I agree the law mower starter deal is fab but I am committed to try to make this work

Re: Derby decomp assembly

What you're not getting is that you shouldn't even need a pull start

with a kit, starter shoes can work fine.

Though I loathe them because of the hanging idle feeling they hold at low rpms.

Will Parrishdirt is running the malossi wc hobbit kit.

No decomp, normal starter shoes.

Starts with one kick.

Re: Derby decomp assembly

Probably right jbot. My stocko shocko will start if I am using it a lot without the decomp.

Re: Derby decomp assembly

Better yet, ditch the bottom ring and ringland port the top ringland and

it's like an auto decomp.

Much less compression until it starts.

All my bikes have that.

Re: Derby decomp assembly

9/64 Circlip found at the woodland orchard supply seems to secure this decomp.

Jbot your level of expertise is so amazing. I will keep your wisdom stored. I borrowed the Athena piston from cheetachrome and he commented that the ring land porting could be improved upon. Now I see yet another reason to get stuff like that exactly right. Wow

But back to this. Next step is to ascertain the head actually fits.

The decomp pathway on the derby is angled where the gases exit to the groove milled into the face of the head. That leaked for cheeta leading him to plug the decomp off. If it leaks there I was wondering if a dab of jb weld would work or drop a dab of metal with a tig.

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Re: Derby decomp assembly

Yea baby!!!!

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