Tohatsu 50D2 carb

[K9Kampers]

I have disassembled, cleaned, reinstalled my three carbs. In my haste, I forgot to document the factory settings of the pilot screws. Does anybo dy know how many turns out from fully seated for the pilot screws for a starting reference for syncing the carbs? Tohatsu M50D2 Automix 2-stroke.

[Don T]

Hello,
Start out at 1 1/2 turns. Any adjustments made with the ear muffs will have to be redone tied to a dock. The back pressure changes and thus the mixture. You'll want to do an extended idle test in gear to make sure it doesn't load up.
Since you had them apart you should make the synchronizing adjustments too.
Do you have a manual? I could scan and send the appropriate pages if you need them.

I made some tubes out of PVC elbows so I can use my Uni-Syn to get it perfect. The linkage has a few adjustments that make syncing the idle, off idle and mid throttle possible. You'll want to check your timing as well. Most dealers misread the idle timing as BTDC when it is actually supposed to be 2.5* ATDC. It prevents that annoying backfire / stall condition.

Here is a pic of the tubes. I had to turn down the pipe diameter to fit in the air box hole.


Here is a pic of the linkage.
The bottom 2 carbs have screws that change the angular differences of the link pin to shaft center (changes off & mid throttle sync).
I added idle screws / springs to the bottom 2 carbs for maintaining perfect idle sync (thus not relying on the interconnect link).

[K9Kampers]

Thanks for the reply Don. I've launched twice last week to sync under load at the dock / in the bay. The best I've gotten is good idle and good headway speed, but just bogs and stalls at higher throttle. I've been starting my adjustments at 2 1/2 - 3 turns ... I'll retry at 1 1/2. I've left all the other timing / linkage adjustments alone and confirmed them against the measurement given in my Seloc service manual. I found a related thread in the archives that mentions the Uni-Syn and have been looking for one locally, but will likely have to order one. I'll follow up with results - thanks again.

[Catigale]

Let me check my old tools to see if I have my old synchronizer left over from my dual carb VW days....pm me your address too...

[kmclemore]

I found a related thread in the archives that mentions the Uni-Syn and have been looking for one locally, but will likely have to order one.

eBay is your friend... there's loads of them out there. Hard to find in a store, though.

http://www.ebay.com/sch/i.html?_sacat=0 ... yn&_sop=15

Rather than three tubes I just made one short tubular adapter for mine that I just move along with the Uni-Syn... works a treat. I've had my Uni-Syn for over 40 years now and have used it to tune the multiple carbs on countless little British cars. Tuning the airflow of multi-carb setups without one is folly.

BTW, the proper name for this tool is a 'manometer'. There, you've had your tool trivia lesson.

=============
On edit - Sorry, Steph, we posted at the same time. Free beats eBay every time!

[Catigale]

Can you get British cars to run long enough to synch two carbs.....

[kmclemore]

Can you get British cars to run long enough to synch two carbs.....

Running since new in 1949. Never restored. Just driven regularly and maintained properly.



(The car, that is).

I rest my case.

[Catigale]

Why are those tyres sunken into that driveway.....

[Don T]

Hello,
Just for grins I'll go out and count the turns on my engine tomorrow and let you know what they are.

[Catigale]

Arghhh....LBCs!!! They are everywhere....!

[Catigale]

Andrew..sent you EM...will this fit in the space on the outboard?

[K9Kampers]

Steph-
I've got 2.25 in. between bolt heads, otherwise I could make adapters as Don did.
(...EM also)

[K9Kampers]

Hello,
Just for grins I'll go out and count the turns on my engine tomorrow and let you know what they are.

Thanks Don, that'd be great!

[restless]

this is heart wrenching engineering chat chaps!
Especially pertinent as my ns502d is still sulking like a witch since it got polluted with filthy greek petrol. Peaches gets really miffed when she's doing cunning manouvres in tight spaces in front of a crowd only to be upstaged by a petulant engine stalling on us!
Syncing carbs takes me back a few years... brit cars? superb!

[Don T]

Hello,
The problem with the bare carb inlet is the difficulty in getting a good seal, especially on the bottom carb. That's why I left the plastic housing on and made tubes to fit it.