Main jet recomendations?

Does your Spree/Elite already run great, and you're trying to make it quicker/faster? Need a monster motor swap? Discuss your ideas here.

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AKAspree85
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Main jet recomendations?

Post by AKAspree85 »

So I am working on an '87 Spree build, not swapping the engine or anything, just doing the upgrades I can to the AF05 to see what she'll do. I am looking for input on what size main jet to use rather than just taking the carb apart 50 times trying to figure out the best one. :wink:

The engine is mostly stock, stock carb as well (other than the jet). I have a UNI dual-stage pod filter and the S23 exhaust from SSS. Based on a thread I found on here, I have a tallboy beer can I can use to cover part of the air filter if needed.

Other minor modifications include:

Intake
Dell'orto manual choke (bystarter delete)
Malossi fiberglass reed

Engine
S23 CDI
Naraku race coil
'84 flat-top head
'87 domed piston

Any ideas on what jet would work best? I have tried a 70 and 72, but both seem to have their issues. Should I go bigger? I have the SSS jet kit so I have all the sizes to try, I just don't want to keep pulling the carb and risk stripping any bolts.

I am waiting on the wheels to come back from being powder coated, then I will post some pics!
Thanks for your advice! :thumbwink:
My babies, '99 Mazda Miata (Henry), '22 Genesis G70 (Sofia), '85 Spree (Lil' Red Riding Spree), '87 Spree (The Rat Rod), '80 Honda XL250S (Barney)
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Re: Main jet recomendations?

Post by Meatball »

CHT needed to avoid meltdown while jetting. Whats equally important with your motor and current setup is the amount of air being allowed in by the air filter. Too much or too little flow would disrupt the air speed in the veturi and the Spree AF05e doesnt react well. Try covering the pod filter completely with your magic beer can and toy around with a series of holes. Sometimes less is more.
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AKAspree85
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Re: Main jet recomendations?

Post by AKAspree85 »

Thanks for the advice! I figured I'd have to cut back the air flow.

Please pardon my ignorance, what does CHT mean?
My babies, '99 Mazda Miata (Henry), '22 Genesis G70 (Sofia), '85 Spree (Lil' Red Riding Spree), '87 Spree (The Rat Rod), '80 Honda XL250S (Barney)
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Re: Main jet recomendations?

Post by Wheelman-111 »

Greetings:

Sorry for elbowing in but nobody's replied to your question since yesterday. It stands for Cylinder Head Temperature (Gauge). These are plentiful and cheap on ebay and presumably other sites. You gots yer 14mm ring that mounts under the spark plug in lieu of the crush washer that comes with the plug. You're on your own routing the wire somehow to the head set. I use Velcro to stick the readout pod and have it removable when you need to dismantle. The best All-in-One gauge is the Vapor, sold at the Swap Shop. It's a bit of a process to install but I don't regret doing it.
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Re: Main jet recomendations?

Post by motormike »

Wheelman-111 wrote: Sat Aug 06, 2022 2:52 pm Greetings:

Sorry for elbowing in but nobody's replied to your question since yesterday.
Negative Wheelman...all comments welcomed at any time.
This is an equal-opportunity forum...motor
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Re: Main jet recomendations?

Post by AKAspree85 »

Thank you all for your input, I appreciate your help with this!

I ordered the Trail Tech temp gauge from Swap Shop as I am keeping the stock gauges in place for now.
Any ideas on the jet size? Really just looking for the best place to start, then go up or down as seems to work best.
My babies, '99 Mazda Miata (Henry), '22 Genesis G70 (Sofia), '85 Spree (Lil' Red Riding Spree), '87 Spree (The Rat Rod), '80 Honda XL250S (Barney)
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Re: Main jet recomendations?

Post by Wheelman-111 »

Greetings:

Stock is 68? Go up a size at least if you're not running the stock airbox. Your bigger problem will be the Idle circuit. "Jet size" is pre-determined by whoever drilled the carb at the factory and cannot easily be upsized.
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"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
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Re: Main jet recomendations?

Post by AKAspree85 »

That seems to be my struggle at the moment. It runs FANTASTIC with a 76... For a bit, then dies and won't start. I'm assuming it's flooding slowly as the 76 is just a little more than it can handle. I just put a 74 in tonight, but I didn't get a chance to test it. I'll let you know how it goes! Thanks again for your help. This forum is a lifesaver! :2thumbs:

Here's some pics of her put together. There's a few things to tidy up but she's pretty much there!
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My babies, '99 Mazda Miata (Henry), '22 Genesis G70 (Sofia), '85 Spree (Lil' Red Riding Spree), '87 Spree (The Rat Rod), '80 Honda XL250S (Barney)
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Re: Main jet recomendations?

Post by motormike »

bazinga
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Re: Main jet recomendations?

Post by AKAspree85 »

Welp... The 74 is better, she'll hit 35 when she's on top of her game! But... She still dies after a while. Longer than with the 76 though so that's an improvement! She'll start up again, but dies if I close the choke or give her throttle. I think she might still be flooding so I'm going to try the 72 again, if that don't work maybe time for a new carb. 🤷

Here's a pic from testing out on the trail by my house!
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My babies, '99 Mazda Miata (Henry), '22 Genesis G70 (Sofia), '85 Spree (Lil' Red Riding Spree), '87 Spree (The Rat Rod), '80 Honda XL250S (Barney)
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Re: Main jet recomendations?

Post by AKAspree85 »

Just a thought, if the 72 bogs on the top end like it was doing before, would a 74 with the needle in the lean, top position maybe work? I may try that first... 🤔
My babies, '99 Mazda Miata (Henry), '22 Genesis G70 (Sofia), '85 Spree (Lil' Red Riding Spree), '87 Spree (The Rat Rod), '80 Honda XL250S (Barney)
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Re: Main jet recomendations?

Post by IvyOperator »

Judging by your mods, try to keep going up. You might be too lean. I have similar mods and I believe 80 worked for me. You might be too lean, causing overheating, and then a soft seize where the motor can't overcome friction. How long/far can you ride before it'll die?
Not sure how to explain why the 74 was better than a 76 though.
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AKAspree85
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Re: Main jet recomendations?

Post by AKAspree85 »

Thanks for the input! It runs worse on the 72 I think. I'll try an 80 and see that happens, fingers crossed.
My babies, '99 Mazda Miata (Henry), '22 Genesis G70 (Sofia), '85 Spree (Lil' Red Riding Spree), '87 Spree (The Rat Rod), '80 Honda XL250S (Barney)
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Re: Main jet recomendations?

Post by Meatball »

Try restricting the air filter. Or even better, put the stock one back on.
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Re: Main jet recomendations?

Post by AKAspree85 »

Meatball wrote: Tue Aug 23, 2022 10:38 am Try restricting the air filter. Or even better, put the stock one back on.
I know Sprees like to be left stock, that's what makes tuning one fun and challenging!

I have a stock '85 that usually tool around on. The '87 was a mess when I got it so I figured it would be fun to mess with rather than try to bring it back to stock. I've learned so much with this project!
My babies, '99 Mazda Miata (Henry), '22 Genesis G70 (Sofia), '85 Spree (Lil' Red Riding Spree), '87 Spree (The Rat Rod), '80 Honda XL250S (Barney)
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