Cool Carb Thread

[sussexscooterhead]

www.buggynews.com/viewtopic.php?t=2152

[sussexscooterhead]

Well, I took the plunge and ordered a Mikuni TM24 from Beatrice Cycle as well as a few jets.

dratv.com/24mmmikuni.html

I also got lucky and came across an aluminum intake manifold on Ebay for $20 with free shipping!!

I'll keep everyone posted with installation pics and impressions.

[sussexscooterhead]

WooHoo!

All my parts arrived the other day and I finished the initial installation this morning.

It was super easy and started right up!

Unfortunately, the weather isn't co-operating and a test ride is going to have to wait for a bit. I'm sure I'll have to make some jetting changes so the spares I ordered should come in handy.

You can check out pics here:

tinyurl.com/jqf29

[sussexscooterhead]

Had a chance to ride briefly yesterday.

Acceleration is improved I'd say 20% and top end is up 10% - 68mph up from 61.

I installed the biggest main jet I had and it's still lean so a trip to the store is in order. With such a big air filter I'm running lean all across the board and will have to get a pilot jet as well.

Stay tuned.

[xtremerpr]

Sounds good keep the updates coming

[somecallmetim]

I'm interested in the final results with this carb once you get the jetting sorted out. I've seen similar "OKO" brand carbs on Ebay. I don't know how the throttle cable would work out though; it seems it would have to come up into my underseat storage compartment.

[sussexscooterhead]

Tim:

I think the OKO is a great idea - especially considering the price on ebay. I think the powerjet is an interesting idea as well although it would be nice if it was tunable like dial-a-jet.

The throttle cable on mine comes up between the stock air box and the storage box so no issues there.

I did cut the end off the stock cable and solder on a new end for the mikuni so you might want to consider that as well. It makes going back to stock a little more difficult.

[somecallmetim]

If I modifiied the cable and then wanted to go back to stock, I could just do it the way we did in my neighborhood when we were kids. We built minibikes out of bicyle frames and lawnmower engines and would tie a length of string to the throttle linkage and the other end to the back of the seat. The rider would reach down under the seat and pull the string. That left the other hand to steer, and there were no brakes to worry about. I became the king of my block when I made a twist-grip throttle from a piece of copper pipe and an old bicycle brake cable, but then was dethroned when another kid aquired a genuine Sears Allstate moped.

[sussexscooterhead]

For anyone interested this guy has both the OKO carb and a replacement cable.

tinyurl.co.uk/egzc

tinyurl.co.uk/r3tl


I've been out of town the last few days and haven't been able to make jetting changes but, hopefully, will be back at it tomorrow.

Pdaddy suggested that perhaps I have an air leak somewhere causing the lean condition so I have checked all the connections and used sealant on the manifold to cylinder joint. The test ride will have to wait until tomorrow.

[sussexscooterhead]

Finally got around to tackling the jetting.

Temps here today are in the low 60s and elevation is 800ft.

Ended up with a #170 main - stock needle in the second clip position from the top - air screw at 2.5 turns out - pilot #15.

I still plan to change the pilot jet as there is a bit of hesitation just off bottom and I shouldn't have to run the air screw so far out. The jets should be in either today or tomorrow.

The scooter pulls noticeably stronger (with the exception of the aforementioned hesitation) and reaches a speed of 56mph on the test strip of road on which it used to be lucky to reach 50mph. I'm a lousy estimator of distance but I'd guess it's about 200 feet with a slight incline.

I've ordered some cheapo 10g roller style weights and a yellow spring and am looking forward to testing everything together because I feel the variator is shifting too soon to get maximum fun factor out of the carb. You can really feel how quickly the engine wants to rev up before the clutch has fully engaged but the low shift RPM of the stock weights and spring load the engine down too soon.

[sussexscooterhead]

Installed a #12.5 pilot and the hesitation just off idle has been eliminated.

The air screw is now at about 1.5 turns out - depending on conditions of the day - which is a more normal range for it.

The needle is now in the 3rd position.

On the whole, I don't think I would recommend this carb. It does improve throttle response and I have seenan increase in top speed but it seems fickle and I've noticed, especially on deceleration, that there are lean spots on the needle that cause it to slow down more quickly for a split second until you're past that throttle position. I'm thinking a needle with a different taper could help with this.

Neither issue is that big a deal but I doubt the average rider wants to be perpetually fussing with things.

Eventually I'd like to install a Dial-a-Jet which should smooth over these inconsistencies and ultimately may come up with an end product that works seemlessly and is easy to adjust but the bottom line at this point is that the TM24 is only for those willing to do a lot of work.


Here's my jetting:

Air Screw - 1.5 turns out
Pilot Jet - #12.5
Needle - 5N13 in 3rd position
Main Jet - #170

[pdaddy]

Good info m8..
Im surten you will get it running without any probs in no time

Marcus

[Darthchile]

sussexscooterhead, I just got a TM28 to play with. I wanted a TM33 pumper, but too expensive. Probvably will get it for Xmas. Until then, I'll use your info to come across a nice config.

[sussexscooterhead]

Cool!

I'm looking forward to hearing how things work out for you.

I heard back from motorcyclecarbs.com about the Dellorto 24mm and 26mm carbs with accelerator pumps - $300! Ouch. Scratch one of those of my list.

[Darthchile]

Look for a TM33 pumper in Amazon, $211 in sale, Sounds like an x-mas gift for myself to me!