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Post by dando127 on Feb 22, 2022 23:30:22 GMT
Need I say more? If originality was NOT a consideration, and you were putting a 292 in an old sled, would you use a perfectly matched Tillotson or a perfecly tuned Mikuni? Why?
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Post by olyman on Feb 23, 2022 17:24:23 GMT
For me and my 292 - I like the tilly because it works, its sitting on my lap for ease of tuning to conditions while riding, and looks cooler than a mikuni any day. Especially with the rubber horn from Spaulding on it. Further to that, I have swapped a pile over to mikuni, and very few have been better. You need an infinite amount of jets and parts to play with to get it actually working good at all ranges and most expected temperatures. Unless you find someone who has perfectly matched a Mikuni to your engine and your exhaust I would be apt to make that old honker to the job. Again, just my 2c.
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Post by ericr on Feb 23, 2022 22:45:15 GMT
I'd run the Tillotson! Jets with a twist of the needle! No vibration issues on a single. Here's what I get tired of on the vintage sled boards on Facebook... a guy comes in and has a Tillotson carb and the typical "won't pull fuel" issue. Two smart folk try to help them out, another says "Throw that piece of shit away and put on a Mikuni" and it turns out the issue was a broken off pick up hose in the tank... So let's say the poor guy goes out and buys the so called holy grail of Mikuni carbs, has to figure out how to get a pulse source on his one lunger Rotax, then finds out he has to change his throttle block on his handlebar because the original throttle flipper won't work with it, and puts one on. It still won't run because his original issue was a missing pick up hose in the tank. .  |
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Post by dando127 on Feb 23, 2022 23:03:21 GMT
This what I was looking for....a good old fashioned debate. And a debate needs two sides. Sounds like short term the tillotson wins, just due to ease of tunability.
What if you had the specs for the perfect mikuni jetting, and mounting and throttle blocks are not an issue. I guess what I am asking is, which one gets the fuel to the engine the best? Is there no difference? Why did ski-doo change?
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Post by olyman on Feb 24, 2022 3:32:02 GMT
What makes a Mikuni nice is its plug and play for systems that have been designed and tested. Draining the fuel out and putting new fuel in the next year is likely going to have far less problems than doing that with a tilly. A properly setup and designed Mikuni should last a really long time with very little to go wrong.
I have one on my 68 299 engine and it runs awesome (though the pilot is a little too rich still).
Gotta say I've had problems with both style carbs, and can appreciate both! If you are going to put one on a single that never had one before make sure you find a way to support it, keep it level, and take the time to set it up. It can be done. Or you can keep it oem and run that tilly in any direction you please 😁
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Post by Doo640ER on Feb 24, 2022 14:39:20 GMT
This is an excellent thread and all opinions are spot on. I can't add much. But what I will say, for me personally the Mikuni's have historically caused me much less angst. With that being said, I'm speaking about the Mikunis on my 81 Citation and 02 Legend. If you keep them clean and treat them right, they seem to be more trouble-free for me. When a cleaning is necessary, it's not very difficult nor expensive.
Now the Tillys on the other hand (and this may just be me), it seems like no matter how kind I am to them, and no matter how much money I spend on a good rebuild kit (from EC Carbs), they just seem to be more temperamental to me. I have more issues with needles and seats sealing, struggling sometimes to get the correct pop-off pressure, diaphragms sitting and getting stiff. It seems that if I haven't used a sled with a Tilly on it for 3 or more years, I am guaranteed to need a full rebuild on it before I can get it running well again.
All that being said, It could be my fault. I have historically used gas with ethanol in it. We all know this is BAD for our toys. I am religious about using Stabil, but I think that only goes so far. I just think Tillys can be more expensive to upkeep.
Seems some sleds are just more finicky with the Tilly than others. I am going to attend a vintage show this Saturday and so yesterday afternoon I went to load up two sleds on my trailer. The 67 Oly and the 72 Nordic. The 67 had not been running in over a week. I put the choke on and gave it one pull. The ole girl fired-up on one pull and purred like a kitten. The 72 640 also started-up easy with the electric start. So I went 2 for 2 yesterday and it was cold in the garage, maybe 25F. I guess I did something right when I rebuilt these two carbs last year. And I am running non-ethanol gas in these two sleds nowadays. Hmmmmm, coincidence??
To answer your question, I would go with the Tilly as long as it is built and tuned properly. Too many times Tillys get the bad rap because cheapo rebuild kits are used and problems ensue.
Here is a short video of the Nordic starting up the other day (not yesterday). This is pretty typical of how it goes these days.
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Post by olyman on Feb 24, 2022 17:34:56 GMT
Excellent points. I should have mentioned that there are definitely more parts to a tilly. There are more things to remember, and when you buy a kit for them, I have yet to find a kit that you can use everything they supply. You definitely dont get the hard to find parts like check nozzles or jet seats etc. Even the needles and/or hi lo jets aren't worth changing if you can keep the originals working. And for goodness sake don't lose the OEM spring either because you will be hard pressed to get the right strength one back in it again. So based on those facts + the tools you should have like a popoff tester... it's a little daunting to many who don't have the experience or access to this stuff
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Post by bones on Feb 25, 2022 22:26:31 GMT
Oh some of you guys are moving to the dark side  . Many of you know my feelings ha ha. I believe if a tilly has all good parts and set right it will doo a good job. Hermit was a great advocate of the Tilly and did a great job of figuring out where to get good parts etc. But.....I doo not think a Tilly can feed the mid range as well as a Mikuni. There is a few Tillies with a intermediate jet which are better ( imo ). If you are working with a Mikuni that was set up by the factory guys I would take that any day over a Tilly for function. For "cool looks" I take a Tilly. If you are trying to install a Mikuni on a sled / engine/ exhaust that was never done by the factory guys,,,,you are in a for long and possibly expensive procedure to get it right. I have a 335 single running a VM34 and a 340 single running a VM38 and I am very pleased. I agree with Eric, many times guys want to throw a Tilly away for reasons that are not the carbs fault, not fair. My vote: Mikuni Bones |
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Post by ericr on Feb 27, 2022 14:28:12 GMT
For a person that is mechanically competent and understands how a carburettor, any carburettor for that matter works, a swap isn't a huge undertaking. However for many on the Elan page or the Bubblenose Ski doo page on facebook, well they bought an old 12/3 or '70 335 and it's got a few hickups. They come in asking specifically for TILLOTSON advice and some asshat just says "Throw that piece of shit on the trash and get a Mikuni" Well, they barely know how to change a spark plug and now based on this they are going to end up with a basket case that won't run at all.
The point is, should someone ask a tech question on a Mik, why like my grandma said if you have nothing to say say nothing. I keep my yap shut!
The old car forums aren't any different, the Holley vs Edelbrock disputes turn to near fist fights. Meanwhile I'm over in my corner with my Quadrajet which runs really sweet. Like any setup on any engine, you have to get it tuned right and it will make all the difference in the world!
I learned carb tuning first messing with air cooled VW's, always trying to get a little more power with swap meet cast off Weber progressives, then going to dual single throats, making my own linkage and learning to synch them just right- then on to bigger dual throat Webers. And a small change in temp would make them run like shit again so yeah after that getting back in to sleds after being away for a decade made tuning and rebuilding a Tillotson a picnic!
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Post by greenandgold on Feb 27, 2022 16:41:45 GMT
I’ll play along as its cold and no real snow at the moment
Back in the day I had a brand spanking new 1975 RD 350. Promptly bought a motorcycle magazine where the main cover story teasers was how to time your duel independent point RD. That’s another story.
In the same issue was a 4 page article on how to ditch the useless OEM Mikunis and put real carbs on it, a pair of HDs…..
Since moving out of the Minn snow belt annual rideable snow isn’t a given. So all the sleds sit. Put away in running condition, always. When it comes time to start 2 to 3 years later, seems to be a very small chance anything with an HD will function well. Better luck with the floaters, although those with very small idle jets often (not always) need cleaning. I drain float bowls before storage, but don’t run Tilly’s dry for fear of a lean condition.
There have been exceptions. Loaned a 71 299 Oly to a guy to relive his childhood desires. He ran it for 3 years, let it sit for 7, eventually wound up back with me. With new gas and a squirt pup started, idled and ran just fine. Maybe the smaller diameter of the diaphragm, better material, or just good luck?
Pumper diaphragms are my main issue. Instead of remaining nice and flexible/pliable, they quickly become stiff and in flexible. Always fueled with non ethanol. At the same time the separate Mikuni fuel pumps seem to run forever; I’ve got some with original 36 year old gaskets that keep on pumping. Combination of crummy gas chemistry and engine heat killing the carb mounted diaphragms?
Carbs on 73-75 F/As are knuckle busters to change, the HS and LS adjustments are a PITA to get to, and the double pull cables on the 73/74s are also getting sticky with age. But all mine still sport Tillys because as Bones mentioned, I haven’t been able to come up with the magic Mikuni jetting/slide combo yet. Fine at some openings, rich or lean at others. Thought of frying scarce pistons always in the back of my mind.
Have some Skunks and a Bullet in the finishing phase of restoration and am struggling with carb selection. Can’t find check valves for the HD 98s/107s/134s awaiting installation. Will likely have to use Mikunis for that reason alone. Getting hard to find any HD check valves, let alone the correct one these days.
Since I gave up Satellite TV due to garbage content, I occasionally surf up Power Nation. They air episodes where two guys rebuild auto engines. Show typically ends with a dyno run segment. They frequently add aftermarket programmable fuel injection to the 60s/70 stuff and comment how they’re becoming easier and easier to use/program. Custom fuel maps and changes on the fly. Maybe someday there will be a EFI body and battery retrofit for obsolete 2 strokers, two wheeled and tracked.
In the meantime if anyone has cracked the code on Mikuni’s for trail ridden F/As or bought a case of check valves drop me a line…..
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. Many of you know my feelings ha ha. I believe if a tilly has all good parts and set right it will doo a good job. Hermit was a great advocate of the Tilly and did a great job of figuring out where to get good parts etc. But.....I doo not think a Tilly can feed the mid range as well as a Mikuni. There is a few Tillies with a intermediate jet which are better ( imo ). If you are working with a Mikuni that was set up by the factory guys I would take that any day over a Tilly for function. For "cool looks" I take a Tilly. If you are trying to install a Mikuni on a sled / engine/ exhaust that was never done by the factory guys,,,,you are in a for long and possibly expensive procedure to get it right. I have a 335 single running a VM34 and a 340 single running a VM38 and I am very pleased.