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Post by ThaiGyro on Mar 24, 2017 4:54:54 GMT -5
I have been working with some karting crazies here in the SE Asia region. They seem to run both 2 and 4 stroke engines. After a little pit wandering and watching to see who-dunnit on lap times, especially qualifying...they nearly all ran a hybrid carb. I have seen these in larger venturi/butterfly valve sizes on airplane engines. Not really a surprise that someone stole the design for racing cars/karts/bikes/boats and chainsaws! The general idea is less parts = less time tuning. As I am a fuel injection nut, it makes sense. If this can make our collective lives simpler, with performance gains, then let me at it. I found a large company in Ireland (Tillotson) who manufactures parts for IAME and other organizations...and another in Italy who does the same. (Tryton) The design is simple-ish, maybe. The carb has a built in pump that takes whatever liquid head pressure is available, using intake vacuum pumps fuel into the venturi after the butterfly valve. In all I have seen, they have a low end circuit and a high end circuit. Each has an external thumb screw operated valve. Because of the higher venturi velocities, you can expect to use a lower size than with conventional carbs. Tillotson says: Anywhere from 2 to 6, depending on required horsepower. That means, for example...if 19mm is near ideal for a good to great performing 50cc, you might expect a 13 to 17mm, depending on other performance installations. We are going to buy a Tryton B18 and test it on a 50cc engine. After a few attempts to find happiness with Tillotson, they seem to be too big for small needs. Their dealer in Asia is just a front for any ones parts. I am a baby boomer who believes in customer support, so doing my own thing again. The Tryton people have told me that they can create venturies to spec, within design limits on larger orders. We will test and adjust as we can afford. What say you all?
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Post by eclark5483 on Mar 24, 2017 4:59:34 GMT -5
I am considering a Tillotson for my next Spree project. I like the idea that they are jetless and can be tuned in with a remote dial. Just have to figure out where I would mount the remote dial and where to get one. I know scooter swap shop sells them, but I need to do a bit more research to make 100% sure I can make it work on an AF05 engine. They are pretty pricey and I don't want to buy one just to find out it won't work for what I want to use it for.
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Post by ThaiGyro on Mar 24, 2017 6:38:48 GMT -5
The "remote' that I have seen is a simple high and low thumb screw...as seen in their pictures... Yes, very pricey, unless you can envision a 14, 15, 16 , 17, 18, 19mm version designed for a chainsaw...can you say "Custom?" I want a version that can sell here in Asia for near $100 USD.
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Post by benji on Mar 24, 2017 9:53:31 GMT -5
Yah there pricey and finicky from what I hear... Constantly twisting the screws. And they are NOT simple. The have a bunch of parts, I have a diagram somewhere... Here it is. Oh, and no choke on them so you gotta cover the carb with your hand to start it.
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Post by ThomasTPFL on Mar 24, 2017 10:44:32 GMT -5
Brandon had a kit for this for a minute, don't know how well it went over.
A friend of mine, from the karting scene, is planning on running a Tillotson in his Yammy engine, but he's been working on chainsaws and such forever so those carbs are familiar to him and he has stuff laying around already he can make work.
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Post by benji on Mar 24, 2017 10:54:55 GMT -5
If you know how to use them I'm sure there fine. But I don't reinvent the wheel. My motor is closer to a dirt bike than a chainsaw, so I use dirt bike parts.
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Post by benji on Mar 24, 2017 11:03:42 GMT -5
I want a version that can sell here in Asia for near $100 USD. Look up "oko" haha. I think you can get 2 for that.
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Post by ThomasTPFL on Mar 24, 2017 12:15:05 GMT -5
Go on eBay and look up chainsaw carbs. You can get Asian Tillotson clones for like $20. You'd have to do some backwards cross-referencing to sort out what chainsaw to search to find the carb you want.
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Post by gsx600racer on Mar 24, 2017 13:20:26 GMT -5
These carbs have been around for years. I have them on all my jetski's, mostly Mikuni carbs. Although jetting adjustments are just simple thumb screw for hi and low there is a "pop off" pressure setting that's crucial for the carb to work correctly. PS: This pop off tool also doubles as a great engine case leak test tool.
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Post by 190mech on Mar 24, 2017 13:43:15 GMT -5
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Post by AtariGuy on Mar 25, 2017 5:46:33 GMT -5
I'm doing some reading on the subject of cv vs pumper/flat slide carbs, and tbh, i'm rather impressed. No lag time on instant wot, and some trail riders (dirt bike forums) even say they're getting better gas mileage too. Now this isn't suggesting i know much, i've only been reading up on these for the last hour. Would this work with premix? Should i look for one with an accelerator pump? And what do i have to look for to find one that will mount up in place of my mikuni i have on my mina? I'd love to find more reading material on this!
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Post by 190mech on Mar 25, 2017 6:00:12 GMT -5
Chainsaws run premix,,its a 'pumper' so it is designed to force fuel into the jets,no accelerator pump needed.Can be mounted at any angle,so it could be bolted right against the reed with a mount plate(shorter intake is always better on a 2T),,the ebay one I listed would likely be a good first try carb..
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Post by AtariGuy on Mar 25, 2017 11:06:06 GMT -5
Chainsaws run premix,,its a 'pumper' so it is designed to force fuel into the jets,no accelerator pump needed.Can be mounted at any angle,so it could be bolted right against the reed with a mount plate(shorter intake is always better on a 2T),,the ebay one I listed would likely be a good first try carb.. i really gotta break my traditional carb mentality, eh? How about the idea that these carbs have a limited lifespan? Someone tried explaining in some blog that lumberjacks would maybe rebuild these once, then replace them? I suppose in our setup, they would last longer, but thats why i'm asking...
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Post by 190mech on Mar 25, 2017 12:33:51 GMT -5
In jetski applications they last many years,I think the pro saw guys replace them to save time.. Here is a pumper setup I was working on for 'Snoopy',never got to try it as the drag races were fading out around then;
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Post by AtariGuy on Mar 25, 2017 13:16:14 GMT -5
In jetski applications they last many years,I think the pro saw guys replace them to save time.. Here is a pumper setup I was working on for 'Snoopy',never got to try it as the drag races were fading out around then; speaking of snoopy, sorry off topic, did you get your belts in yet? I'm excited to hear more updates!
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