Alky Sudam conversion

Attack2001

Attack2001

Member
Hi guys, got a Sudam here over the pond, not a great deal of info over here, or on the web for that matter. I'd like to convert it to Methanol but i know it's not just a case of filling the tank with the stuff!

Could anyone outline what needs to be changed and adjusted to run a Sudam on meth?

Thanks very much, Thomas......
 
Brian Montgomery said:
You will need to advance your ignition timing, re-cc your head, change you port timing, and have your carb switched to alky or depending on your rules buy a set of dual carbs or one big one. Carburetor Accessories | Idaho | Competition Carburetors Dustin Stephenson, does a wonderful job setting up carbs for many different applications
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Thanks Brian, is the port timing a must or will it run just fine on standard porting?

The regs for our Open class are minimal, open tyres, minimum weight... that's about it.

I'm a 4s Biland man myself, started out on 2strokes when i was a kid. Because of my lack of 2s carb experience i was going with the single big carb to keep carb adjustment to it's simplest. What carb model is the single 34 Mikuni I should be looking for?

Thank you
 
Port timing is something I was wondering about as well ?
Even changing the head cc's .
Are they designed to make max power with the fuel change ?
 
Attack2001 said:
Thanks Brian, is the port timing a must or will it run just fine on standard porting?

The regs for our Open class are minimal, open tyres, minimum weight... that's about it.

I'm a 4s Biland man myself, started out on 2strokes when i was a kid. Because of my lack of 2s carb experience i was going with the single big carb to keep carb adjustment to it's simplest. What carb model is the single 34 Mikuni I should be looking for?

Thank you
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It will run fine without open porting but you are leaving HP on the table. As far as tuning 2 strokes on alky are very forgiving, you can be 1/4t rich and not give up but a 0.1hp, you just got to keep it cleaned out. If you want to go with a single Tillotson now makes a 35mm and I would have Dustin do it for me if I was you. Dual 360's are pretty much standard here for Sudams, of course we stroke them as well. There is so much you can do to these engines you just need the budget to do so.
 
I have no experience with Sudum, but I have a lot of experience with the McCullough 101 reed valve 125 mL. It used a carburetor of a similar size. One thing different, it was a double pumper design. Seems like I've seen a carburetor similar to the one you're using that uses a double pumper. More than enough capacity for alcohol.

Be careful with the inlet needle if it has a rubber tip. Some will swell up in alcohol. I had that problem with the Mac 91 100 mL. I used to keep 2 or 3 in a small glass jar filled with alcohol. When they would swell up, I would put them in my high-speed die grinder and file down the rubber tip to the original size. And left in the alcohol, they would stay that size.

Something else, modifications, you can do them if you want, but there's no need to do anything. With McCullough 101, no modifications were allowed. They ran just fine on alcohol. Not that you couldn't modify one and make more HP, but it wasn't required to run alcohol. Of course you couldn't modify them for the stock class.

Watching the Indianapolis 500, I hear them talking about full rich and lean. They run alcohol. They run faster when they're set to rich rather than lean, although they run just fine in both settings. Alcohol has a much higher tolerance to detonation in a lean condition. Just be aware of this fact. Lean is okay, but full rich is faster. Also be aware of the fact that the oil in the fuel can detonate if you get too lean. It tends to sound like there's something loose in the pipe. A strong rattling noise. I preferred the EGT for detecting a lean condition. You folks across the pond might be aware of that fact. It's not well known here in the US.
 
If you do use a Mikuni BN34 do not use the stock fuel cup on the pumper stack. Alky makes them shrink up and suck air. The Tilly ones will work fine on them or get a nice aluminum cap.
 
Thanks for the help so far guys, all the stuff i need to start taking in. I can get a 34mm X30 Tilly carb over here i think so I'll have a hunt around.

Need to get some specs on the squish and timing if anyone has them? I see lots of variation from 85 to 100 BTDC
 
Yeah, I guess, There's no need to take the factories word for anything, especially when you have such expertise here on Bob's.

My experience with IAME,, nobody does it better. Then them.
 
I once sent a barrel in too some hot shot for port work .
Thing ran worse then when I sent it in .
There's no turning back at that point .
 
Thomas,

My thoughts would be just to run it with existing compression and port timing for now. Get the carb worked out first, as that's the most important.

Once you have your new carb figured out for methanol, you could probably raise the compression a fair amount. (I would do this by measuring cc's in the combustion chamber). Keep the squish band as it is initially. I would avoid doing any port work at the moment -- as others have mentioned, it's often possible to make things worse rather than better. Also note that if you change the port timing (especially blowdown), a different configuration exhaust pipe might be required to take advantage of possible porting gains.

If you plan to leave the engine together after running it, I would highly recommend "flushing" the engine with a typical gas/oil mixture after you're done running for the day/weekend. Letting methanol sit on certain types of aluminum parts can cause corrosion. A 500ml bottle of gas/oil mix with a hose you can connect to your carb is all you need. Start the engine with that connected, and be ready to quickly turn in the jets as soon as the gasoline gets through the carb as the engine will go very rich on gas. Run it for a minute or two on that gasoline, and the engine will be good to sit without taking it apart.

PM
 
Pete_Muller said:
Thomas,

My thoughts would be just to run it with existing compression and port timing for now. Get the carb worked out first, as that's the most important.

Once you have your new carb figured out for methanol, you could probably raise the compression a fair amount. (I would do this by measuring cc's in the combustion chamber). Keep the squish band as it is initially. I would avoid doing any port work at the moment -- as others have mentioned, it's often possible to make things worse rather than better. Also note that if you change the port timing (especially blowdown), a different configuration exhaust pipe might be required to take advantage of possible porting gains.

If you plan to leave the engine together after running it, I would highly recommend "flushing" the engine with a typical gas/oil mixture after you're done running for the day/weekend. Letting methanol sit on certain types of aluminum parts can cause corrosion. A 500ml bottle of gas/oil mix with a hose you can connect to your carb is all you need. Start the engine with that connected, and be ready to quickly turn in the jets as soon as the gasoline gets through the carb as the engine will go very rich on gas. Run it for a minute or two on that gasoline, and the engine will be good to sit without taking it apart.

PM
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Thank you, and to everyone else, getting more info here than anywhere else on the web, much appreciated :)

So i can sling a 34 carb on this and just add the Methanol. Carb settings will need to be adjusted obviously, will the Ignition timing need to be adjusted or only once the compression gets raised?

It's an air cooled lump, I'd like to convert it to a WC setup later on because i think the old IAME Reedjet engine is one of the most iconic 100cc lumps out there, but for now the meth will certainly keep me from seizing the thing.

Thanks very much, Thomas.......
 
You won’t be able to take an IAME/Tryton euro carb (even though the Venturi and throttle bore size is correct) and run alcohol just by running the needles out unfortunately. It needs the high volume double stack, proper diaphragms, passage work proper needles/seats with different pop off and fulcrum height settings. I highly recommend getting an alcohol purposed 34mm from Dustin at competition carbs or from EC Distribution. It will save you a lot of tuning headaches and possibly a piston. The ignition advance will help regardless of compression but CC’ing your head and getting some more squish is where the power is. Compression and advance is the golden ticket on alcohol. IMO your best move is running the sudam in DD with a 34mm alky carb, some added compression and advance with a good flowing direct drive pipe. Can’t remember who did it but there’s videos on YouTube of a guy who ran a full 9 yards buller 131 sudam in direct drive with a direct drive pipe and that thing HAULED against the KZ/Honda shifters and wankles.
 
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Attack2001 said:
Thank you, and to everyone else, getting more info here than anywhere else on the web, much appreciated :)

So i can sling a 34 carb on this and just add the Methanol. Carb settings will need to be adjusted obviously, will the Ignition timing need to be adjusted or only once the compression gets raised?

It's an air cooled lump, I'd like to convert it to a WC setup later on because i think the old IAME Reedjet engine is one of the most iconic 100cc lumps out there, but for now the meth will certainly keep me from seizing the thing.

Thanks very much, Thomas.......
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Not necessarily. In fact I have suffered more piston issues and stuck engines on methanol than on gas. IMO the engines/carburation seems to be more predictable and easier on gas than on methanol despite the higher temps. I rarely stuck any of my 2 strokes on gas unless the piston was old and should have been replaced but I have on methanol. I would also be careful with running much timing advance because it will be hard to keep temps low and you will have a lot of issues with pistons and rings. You should be able to run 85 on methanol without any issues, at least on a stroker 131 I do. Check flex, this is very important. i usually run a KB06 pipe.
 
in high temp. the methanol will keep it cooler , contact a builder here in the states and buy his spec. sheet and get a good builder to work on yours [ get the work done for the spec. sheet ]
 
Pete_Muller said:
Thomas,

My thoughts would be just to run it with existing compression and port timing for now. Get the carb worked out first, as that's the most important.

Once you have your new carb figured out for methanol, you could probably raise the compression a fair amount. (I would do this by measuring cc's in the combustion chamber). Keep the squish band as it is initially. I would avoid doing any port work at the moment -- as others have mentioned, it's often possible to make things worse rather than better. Also note that if you change the port timing (especially blowdown), a different configuration exhaust pipe might be required to take advantage of possible porting gains.

If you plan to leave the engine together after running it, I would highly recommend "flushing" the engine with a typical gas/oil mixture after you're done running for the day/weekend. Letting methanol sit on certain types of aluminum parts can cause corrosion. A 500ml bottle of gas/oil mix with a hose you can connect to your carb is all you need. Start the engine with that connected, and be ready to quickly turn in the jets as soon as the gasoline gets through the carb as the engine will go very rich on gas. Run it for a minute or two on that gasoline, and the engine will be good to sit without taking it apar
Click to expand...
Just curious, why turn in the needles when it gets over to the gas mix? I leave mine where they’re at for alky and just have a dedicated purge plug I don’t care about fouling. It runs like garbage from how rich it gets at the changeover and could smoke a flock of geese out of the sky, but it seems like you’d want to make sure every bit of alcohol and castor gets flushed and a nice amount of marvel and quality gas gets left behind. Does turning in the needles just help save you from fouling a plug or is there more to this?
 
Pete_Muller said:
In my experience, it can be difficult to keep the engine running if the jets aren't turned in at least somewhat.
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It definitely is. It will fight tooth and nail to rev up. But is my logic flawed when it comes to loading the thing up with purge mix to ensure all the residual alky mix is chased out? Or will that much marvel and gas actually harm the carbs after sitting?
 
No flaws in any logic. I just personally prefer to run the engine for a few minutes at modest RPM (just above an idle) rather than try to "keep it running" when it's very rich.

I also only use the same oil in the gasoline that I use in methanol (pure castor), and never run a different oil in the gas.

I would typically put a hotter plug in to do this as well -- one that I set aside just for "cold morning starts", or when I'm flushing the engine.

PM
 
Once again you guys are a great help 🙂

I've been looking through the various carb distributors you guys have out there, your carb prices are crazy! Good 24mm 100cc FA carbs are half the price over here 😂 I will endeavour to try and get one of the companies to give me a run down on the parts and processes to strip and rebuild a tilly over here for methanol. I don't think i necessarily need a special blueprinted carb as it's not got to have every last 0.1hp strangled from it.

I did speak with Buller a few months ago, who i believe are the go to guys in the US for Sudams? I wanted to buy a pair of crank halves to build a Sudam up but they just stopped replying to me, even after a follow up email which left a sour taste unfortunately.

It's nice to talk to guys who know about these engines, thanks very much
 
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