carb changes

Sean Reisdorf /

I hope some of you ventren ped owners can help.

I have a 1978 Puch/Sears Free Spirit.

The bike came with 1/14/xxx carb

I've found some parts I needed, but others are hard to find.

Therefore I've started looking for new/used carbs on eBay and other sites like this one.

The problem is that most of the carbs are 15mm or 12mm

Therefore, what will I have to do to modify these carbs to fit my ped.

I'm "assuming" that the difference in the carb sizes comes from the intake size.

Therefore, if I bolt a 15mm carb on my bike that uses a 14mm will I have to step down the metting jet and/or adjust the float level?

Please cc any replies directly to my work address... sreisdor@ford.com

Thanks in advance!

Sean

Re: carb changes

"Therefore, what will I have to do to modify these carbs to fit my ped."

You'll have to do what you have to do.. that could range from nothing at all to drilling oversized mounting holes to custom-casting an aluminum adapter..

"I’m "assuming" that the difference in the carb sizes comes from the intake size."

Carbs are of a particular size for many reasons, mostly related to reliable performance under the conditions for which the manufacturer of the bike thinks the bike will be ridden.

The "size" of a carb (in millimeters) that you mention is that of the venturi near the main fuel jet.. This is the smallest diameter of the carb's throat and has nothing to do with any intake (whatever you meant by "intake").

" Therefore, if I bolt a 15mm carb on my bike that uses a 14mm will I have to step down the metting jet and/or adjust the float level?"

You may as well ask "If i go fishing, will i catch a fish?" Despite all the books and knowledge and advice available, nobody in this world knows what will happen. Your bike/engine is unique. You are modifying it in a way that nobody can predict the results.. Generally speaking, i could give you some useless theoretical advice about carb size and jet size and float levels but that's just a waste of time.

Find a carb closest to stock. Do what you have to do to bolt it on. Read and learn. Buy some new spark plugs and do 'plug chops' to determine rich/lean mixtures at different RPMs . Study. Examine things.. Study some more.. Test ride the bike. Do some more reading. Determine whether it runs the way you want it to or not. Learn how you can modify it's behavior if you choose to. ...........

BTW, any given carb has only one proper float level.

Re: carb changes

you'll just need to spin in the right size jet

not a problem

Re: carb changes

Sean Reisdorf /

Here is what I've learned...

Someone told me that the Sear's peds came with 12mm carbs.

The only way to tell for sure is to removed the intake and inspect the intake opening on the head.

If it is round then 12mm was stock.

If it was square, then 14mm or 15mm was "normal"

Mine was square, a trapezoid actually.

Therefore the 14mm cabs I have are correct.

However, I'm still having a hard time finding 14mm carbs, so I'm going with 15mm.

I'll be jetting it smaller I'm sure because I'll be reusing the 14mm intake.

Plug chops will tell me for sure and I'll let you know the results as they come!

TTFN

Sean

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