High-Performance Carb For Mitsubishi Engines

I worked on my WYK-58 install yesterday.

An adaptor for a WT-butterfly-style carb was ordered from partsforscooters.com It is a simple .125" thick aluminum plate with intake port, pulse hole and bolt holes. It included two paper gaskets and two bolts, cost me $16 with shipping.

Darn, the adaptor won't work on the TLE43 engine, even if I used the WT carb.. This engine's manifold is dual-port/over-under like a shotgun rifle's barrels. The adaptor bolts directly onto the mani, but its port and pulse hole don't line up with the engine, not even close.

The manifold's top port feeds gas mixture to the engine thru a single reed valve. The bottom port is a straight shot of air thru the engine block to the piston.

:unsure:I need to fabricate a TALLER thicker adaptor and drill it to match carb, pulse hole and manifold. The adaptor will also block off the lower port completely.

:unsure:THENNN, instead of fabbing an external pulse line, I groove a passage from the adaptor's pulse hole to the 13mm(?) air port that matched the original carb's 13mm(?) air port.

That way the original manifold is left intact in case I reinstall the stock carb.

It SHOULD work.:geek:
 
I would think that if you don't care about the scavenging aspect of the TLE43, you could provide the fuel-air mix to BOTH the IN ports.

According to Mitsubishi's documentation, the TLE43 allows air-only to enter the cylinder during the initial intake portion of the cycle; this air gets pulled through the engine and exhausted with the remainder of the burnt gases. By only allowing air in the early portion of the cycle, it cuts down the unburnt HC emissions. By a LOT. (20% to less than 5%)

If you wanted to keep this (it also improves fuel efficiency, if you're not tossing unburnt fuel out the exhaust) you could probably add a separate air-only tube (filtered) at the air-only port. Either route this tube around the carb to the air filter, of add a second air filter. (this one wouldn't have to be as big, I wouldn't think)...
 
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I wish they made intake manifolds for this engines, but I can't find any.

Unsure if this BladeZ mani fits, but it accepts the carb I have. The pulse hole lines up and should be no problem drilling the 1/4" aluminum plate to match.

The 1/4" aluminum plate will mate the BladeZ mani to the engine block. The stock manifold has a single reed, which I will try to bolt onto the 1/4" plate.

The BladeZ mani has a 15mm carb hole and hopefully under that is an open plenum. First I'll drill the plate to 15mm, near where the engine's original manifold's top port is located. If that doesn't work well, the 1/4" plate can be hogged out to match the BladeZ's plenum.

Here's crossing my fingers that everything works well.:cry:

Why am I making such effort to add high-performance carbs? Well, ADA S1 expansion pipes were installed for more power. However this resulted in a lean condition which needs a richer gas mixture.:geek:

Sadly, the Mits engine original carbs are not adjustable, That is why high-performance carbs with low/high speed mixtures are necessary.
 
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One other option is to just run a WT-603 and then tap the case/carb to run the pulse
externally....
Much easier, imho.....
You tap the case anywhere you like,
then tap the bottom of the carb with 10/32 threads and connect hose barbs to both, running tubing between them.

This way, all you have to do is get the carb attached
and you're done!

http://www.capturedbyrobots.com/images/603cagped.jpg
 
Not quite, captured.

I have the WT/WA carb adaptor with a pulse hole.

HOWEVER, the TLE intake manifold is not like any normal intake. It has two 12mm intake ports, over/under like a 410 gauge shotgun.

There is NO way any adaptor for the WT/WA carb or any carb will match ports with the TLE.

I've brought that up at least twice.:confused:
 
Can you post a pict of the setup?

I meant that it doesn't have to match exactly......as long as you block off
a section with a blockoff plate or epoxy it closed, you'll be set.
It would be similar to adding an HP carb to a Zenoah Geo motor.
Those geos have the same style ports.

The modding folks used block off plates and removed the reeds
to use the larger carbs.

Sorry if I was misunderstood.
 
hi 5-7...

most of this topic is over my head...but, have you looked at any of the intakes used on the mitsubishi clones? i think the one on mine would fill the gap you're trying to bridge, because one of your attached pics seemed to be the exact carby i have. maybe i'm wrong, trying to help is all: http://www.motoredbikes.com/showthread.php?t=19457

you can go to the regular scooter-parts sites to get some good pics.
 
the port setup is exactly as 5-Heaven mentions. One port over the second one. Almost like the number 8

One port admits nothing but clean air to the engine - it's used in purging the burnt exhaust gasses. The second port carries the fuel-air mix, and starts entering the cylinder a little after the clean purge air.

With 2-stroke engines, a fair amount of the air that enters the engine during the first 5 to 10 percent of the exhaust cycle gets exhausted along with the burnt gasses. IF there's fuel mixed in with this air, then it gets exhausted from the engine, unburnt. This process, of air going straight through the engine, is known as a short-circuit, as the fuel-air mix doesn't get burnt. it 'short circuits' the combustion phase. This, of course, raises the unburnt hydrocarbons to high levels. By allowing air (only) in the first part of the air intake, the unburnt HCs are much less.

This is the reason for the dual ports in the Mitsubishi engine.

Now, you could follow two approaches to adding a HP carb to this engine, I would guess.
  1. Run two, separate feeds to the engine. One with the carb, and one that's just a pipe to the air filter. (or, use a separate filter.) This approach will maintain the design integrity of the engine, and keep the pollution down and the fuel eficiency up. It IS a more complex design, though.
  2. Ignore the benefits of the clean-air purge, and have the carb supply both ports. Yes, it will cause the motor to emit more HCs, (and, will drop fuel efficiency by about 10%) but, it should work, and it is certainly the simpler approach.
You may still need to supply a separate pulse line from the crank, though.
 
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captured, no apology needed. :D

There would be major restriction if I just bolt the carb and adaptor onto the stock manifold. It would be similar to center an "o" directly over an "8".:geek:

Like most experiments, ya just gotta try it.

augidog, thanks for the tip. Lou, thanks for the explanation.

Does anyone have a picture of the clone's intake manifold?
 
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