Jetting - Model 94 with reed valve

[BrianZ]

I recently obtained a model 94 Wombat engine. This engine has been modified with the addition of a DH Enterprises reed valve and the associated cylinder porting. The engine did not have a carburetor when I got it, but I have a model 94 carb in my stash of spare parts. Does anyone have any suggestions as to what jets I should install as a starting point for jetting this engine?

Brian

[racerclam]

First of all , does that carb have the spray bar prutruding up from the venturi ? Early wombat carbs did not and to get that to work properly you msy want to install a UFO in the slide so that the needle jet can get some shrouding to pull fuel out properly. Other than that normally when going to reeds you will need to go up maybe 6 or 8 sizes from stock to compensate for the weak signal from the reeds being between the crank case and the carb , you may also need a richer needle. Pilot jet will be determined by where your air screw wants to be to idle and not hesitate . You would be better of if you could find an early super rat 24 mm carb (RARE) or better yet a 26mm flange mount carb.

Rich

[BrianZ]

Thanks for the reply Rich. The carb is the later carb with the spray bar. I pulled it out and realized that I had robbed a few parts for another project so I need to find the top cap, floats and a main jet holder. No problems though, I have lots of time to scrounge up the parts as this project will take a while to complete. Since the motor is intended for a trials bike I don't want to go to a bigger carb in case it takes away from the lower RPM torque. Anyway, once I get things together I'll go with richer jetting you suggested.

Thanks,

Brian

[racerclam]

Hey Brian , I just tore one of them carbs apart yesterday , its junk but if you need a part or two let me know and I will send them to you, the floats are junk as well as the float bowl , the cap is good and the main jet holder.
Also Port work can be done to really enhance throttle response and bottom end grunt .

Rich

[BrianZ]

Thanks for the offer Rich. I managed to find a carb top and jet holder, but I still need the floats. I'm pretty sure I can scrounge something locally though. As for porting, I need to get the rest of the bike completed before I can consider it. Gotta put the horse before the cart!

Brian

[Pep]

Hi Brian - I’m bringing this topic to the top because I have an identical situation (94 engine with reed set-up and associated porting).
I found a 24mm Rat carb in my pile and started digging through some notes on a past project (reeded/ported chrome tank Rat with 24mm Rat carb - had a Webco head)
Looks like I had luck with a 230 Main, 30 Pilot, 2.0 Slide, and 4E1 Needle. No notes on the float valve or needle jet (doggone it!) so I assume it was stock (bike is long gone now).
I have a vague memory that the set-up was probably still on the rich side, but maybe this offers a decent starting point. Notes on bigger mains and pilots refer to the bike as way too rich.
I might be off-base, so experts please chime in. Elevation out here is about 1200 feet.
I suspect I’m at least a week or three from running this engine, I’ll update with a progress report at that time.
Thanks,
-Laurie

[joebat]

When I had the Wombat VM24-B carb on my reeded 94:
pilet jet (#25)and needle jet (N-8) were still stock size and the stock needle (4E1) set 1 slot? or maybe the last slot? (don't remember which) to the richer side. Main jet 180.

Joe

[Pep]

Tuning result on my mo-chine (94 engine, reeded/ported, with Circle F pipe, 24mm original Rat carb, and a K&N style filter)
This bike is happiest with a 35 Pilot, 220 main, and clip at #2. The rest of the carb is stock. Nice pale milk-chocolate plug, pulls strong everywhere.
I'm guessing that exposed air filter is a reason why it needs things a little richer than others might.
I highly recommend dropping a big engine into a little Ace 90 - results are too much fun!
-Laurie

[BrianZ]

Thanks for the information Laurie and Joe. I have scribbled your suggestions on a note with my engine, so when I finally get it running I have a baseline to start jetting.

Brian