juan juarez

Hi all, long time lurker that finally decided to make an account. I've alway been a fan of rotary engines and they are very interesting to work on.

I am in the process of refurbishing a long travel dual sport Sandrail that my parents have owned roughly 10 years. They purchased it from a guy that swapped the old vw engine out to this 13B that is currently in it. It was so long ago that any information he did give us on the engine is long gone.

Too Long Didn't Read:
Not much prior information on the engine and build. A lot of recent maintenance and carb rebuild. Current Carb setup:
Weber IDF 40 unknown jetting ( no markings on the jets when rebuilding)
2mm holes in throttle blades, idle speed screw 1/2 turn in, idle mixture screws roughly 1 turn out each, air bypass screws about 1/2 turn open.
Symptoms:
idles well, revs slowly well and revs up to redline well. punching throttle quickly hesitates, stumbles and bogs. if I punch the throttle hard, it will kill the engine. Seems like transition from idle circuit is too lean, but I could totally be wrong.
Help!


Here is what I do know from spending the last 2 months going through it:
1985ish 13B. At least the distributor(electronic) matches that era.
custom(part Cartech, Im assuming) turbo kit with a Weber IDF 40 Carb
MSD 6al ignition on the leading plugs, trailing still hooked up to the distributor
New fuel system with Carter 3 psi fuel pump, Aeromotive fuel pressure regulator and nylon braided lines.
New NGK spark plugs with wires, cap and rotor
Rebuilt carb with jetting that came with it

So here is where I am at. The engine always ran fine with the Weber IDF except when off roading through heavy bumps / woops. It would stumble and bog. Besides that it had great throttle response and power. I figured it was a float issue so I decided to rebuild the IDF 40 (yes its an IDF 40, its stamped near the flange. From what I have read, Cartech kits came with the IDF 40). I started doing research on the rebuild and tuning process and I believe I understand the principle behind it pretty well. Before removing the carb and tearing it down, I took notes on the previous tuning: air bypass screws all the way closed(seated), idle mixture screws all the way closed(seated), idle speed screw about half turn in. Obviously this doesn't sound right according to the best practices.

I tore it all down, cleaned and rebuilt it using a decent kit I found on amazon. I went through the lean best idle practices to get this thing running again: half turn on idle screw, 1 turn on each of the mixture screws, and the bypass screws all the way closed. It ran way too rich and I could not get it to idle well. After reading many conflicting posts across different forums and engines, I was a common suggestion was for single setups was to drill 2mm holes in the throttle plates. So I did that, and got a lot closer, it would actually stay idling but rough. If I cracked the air bypass screws, it would start smoothing out. With this combination, it idles very healthy and sounds great. Now the problem is that the transition from the idle circuit to progression it stumbles and bogs if I punch the throttle too hard. If I rev up slow, it revs great to infinity. It smells just rich enough now to feel good about it not being lean at WOT.
If there are any carb turbo gurus here that could help, that would be amazing. For now, I would rather not jump into a bigger carb as many suggest. At that point, I would heavily consider doing a FI IDF throttle body or pulling the engine and putting a truck LS in the car.

juan juarez

Seems like the lack of responses means the carb gurus might be retired.

I bit the bullet and ordered a 48 IDF. Let the fun begin. I will update in detail as I go to help the next person in this day and age.

diabolical1

iTrader: (3)

welcome to the board.

all else being equal, that 48 is probably a step in the right direction.