Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Hello everyone,

I am new here, but I am not new to mopeds or small engines. I am going to be upgrading my Tomos Sprint with a 70cc cylinder kit and biturbo exhaust. I am keeping the stock carb and gearing. The engine is an A35. I would like to know what size carb jet I should use.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

No one can answer that for you. There's to many variables to consider.

Start by checking out the tuning spread sheet in wiki to get an idea where to start. Then pick up some jets in that range and trial and error until you have it running well.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Walker Quine /

I did look at the chart, but the jets people are using for the 70cc kit range from the 60's all the way to 94, and I read on here in another thread that someone intentionally tampered with the chart, so I really don't trust it. I was hoping someone here would have somewhat a better idea.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Id like to help but Vespas are all I know about.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Go high seventies and work your way down.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Walker Quine /

All right then, fair enough.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Walker Quine /

I was going to get both the 70 and 80 kits and work my way through those, seems a bit of a waste but since no one has any idea what size jet I should use it seems like the best solution.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Jonny Appleseed /

i've also found the tuning spreadsheet to be fairly inaccurate and unreliable. I'm running a 78 jet in my 70cc A55 airsal with the stock 14mm PHVA carb, however it does seem to be a little rich. I think i'll downjet to a 76

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Walker Quine /

Thank you for the response, I am just trying to avoid wasting money on carb jets I won't use, but I would rather run rich than run lean and risk damaging the engine.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Jonny Appleseed /

Yeah I hear you man, I'm in the same position

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

The spreadsheet is totally all over the map. If I were you I would start in the mid 80's and go down to like 65, I don't think that you will end up in the 80's but it won't hurt to start there. Got a a35 65 cc performance pipe stock carb performance air filter and I'm at 65 with the plug looking good.

Re: Upgrading 2005 Tomos Sprint to 70cc kit, what size carb jet should I use?

Walker Quine /

Allright, thanks for the info.

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