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Post by dacota25d on Feb 2, 2015 14:23:44 GMT -6
Just looking to see what kind of rpms can a stock 440 tohatsu crank handle. 8..9..?
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Post by dankubista on Feb 2, 2015 15:58:39 GMT -6
Definitely fine at 8 but the thing to remember is any crank can let go at 9 even racing cranks. There's no for sure thing once you go 9 and above. You could build 10 engines all the same. Some will run 9200 all day. Some won't last one ride. ......2 strokes, awesome when they work. Lol
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Post by dacota25d on Feb 2, 2015 17:04:18 GMT -6
That's interesting I wouldve thought a crank built for racing could handle 9-10 but then again what do I know I'm just a stupid kid haha
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Post by Ruppsforever on Feb 2, 2015 17:32:13 GMT -6
Which 440 motor are you talking about ?? 73 Magnums spin over 9000 stock.
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Post by dacota25d on Feb 2, 2015 18:01:32 GMT -6
72/73 S crank with SR top end
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Post by racingelvis on Feb 2, 2015 21:28:40 GMT -6
tohatsu cranks are not very strong at all. I have a ton of experience with them and I can tell you this, for any type of racing or high revving, they should be pressed apart, a bigger pin pressed in and then welded. they are very light weight and very efficient motors. they always ran good for me and I won a ton of oval races with them. we just got to the point we made way more power than the motors where capable of handling. the tohatsu 650 3 cylinder crank was the best crank they ever made. don't think to many of them are laying around, lol,....
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Post by dacota25d on Feb 2, 2015 21:32:20 GMT -6
Interesting. What's done to put a bigger pin in? Ream the hole out or what?
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Post by racingelvis on Feb 2, 2015 21:57:51 GMT -6
we used a ski-doo pin that had to be faced off to the same length of the tohatsu pin. the tohatsu pin pressed out like at only 8 ton. with the ski-doo pin pressed in it went up to I think it was around 14 ton. normal cranks of today are around 20 to 24 ton to press them apart or together. if your interested I can pass all the info on to you.
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Post by racingelvis on Feb 2, 2015 22:00:19 GMT -6
if your just going to burn around, have some fun, turn some R's, then I think a good crank guy could true your crank up and weld it. that would be fine i'm sure
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Post by dacota25d on Feb 2, 2015 22:02:32 GMT -6
Well I'm looking to drag race it so I'd like it to be good haha I don't want it to fly apart the 3rd run or anything. Yea id be interested for sure
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Post by dankubista on Feb 2, 2015 22:53:00 GMT -6
Long durations of wide open throttle is what is the real killer on engines. What Bill is doing "oval racing" is probably the most taxing on any engine, even the new ones. If you want it to be as bullet proof as possible, Bill knows his stuff with those tohatsu engines!
If you do plan to drag race it, you may find that your pipe, porting combo may not make the best power at an extremely high RPM anyway. (You will need to do testing on the ice) Oval racers need high RPM to keep momentum....drag racing, you need to squeeze every ounce of torque that motor has. 2 strokes, depending on the combination, can literally fall on their face in a difference of just a few hundred RPM. Once you go past the limits of the pipe, you will feel it, you'll know. Expect to do many test sessions and good luck!
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Post by dacota25d on Feb 3, 2015 6:29:24 GMT -6
Yea I figure a lot of testing will be needed. I'm honestly not sure it will be the best choice of sled to race especially against them damn yamis. I feel there's a huge disadvantage and a lot left on the table with the secondary clutch if I could get a clutch with some more adjustability I think that would really help. but reguardless I just wanna see what one will do. Don't see any out there so it'd be fun
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Post by snosnake on Feb 3, 2015 9:27:37 GMT -6
DaCota
Go with the 71 Magnum or 72 Nitro. If you are just starting out stick with stock for a while. Use the Ram Horn exhaust and spin it at 8200 RPM.
The crank will handle it at that RPM all day long and you will pull your best times at that RPM.
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Post by dacota25d on Feb 3, 2015 9:38:40 GMT -6
I'd like to start with a 72 nitro to begin with and start learning stuff. Is the 72 motor better then the 73? I'd like to think so with the finger porting either motor I'd have ram horn on
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Post by kronnikracing on Feb 3, 2015 11:35:18 GMT -6
DaCota Go with the 71 Magnum or 72 Nitro. If you are just starting out stick with stock for a while. Use the Ram Horn exhaust and spin it at 8200 RPM. The crank will handle it at that RPM all day long and you will pull your best times at that RPM. Wow, 8200 rpm? Wonder why rupp had 7200 rpm on all their advertisements. |
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Post by snosnake on Feb 3, 2015 12:54:56 GMT -6
Luke it's called Warranty
DaCota the 73 jugs are better but if your going to race stock use the 72 jugs. That way when you win and they tech you you will not get DQed.
the exhaust is the main thing.
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Post by dacota25d on Feb 3, 2015 14:19:18 GMT -6
What makes the 73s better is the porting better?
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Post by kronnikracing on Feb 3, 2015 14:28:11 GMT -6
Luke it's called Warranty DaCota the 73 jugs are better but if your going to race stock use the 72 jugs. That way when you win and they tech you you will not get DQed. the exhaust is the main thing. Rick i built a 440 tohatsu with some porting about 2 years ago and one of these days the plan is to bolt it up into our dyno chassis and make a couple pulls with 72 exhaust, 73 magnum pipes, maybe the junk 73 nitro pipes and maybe a custom exhaust just out of pure curiosity of what the different pipe rpms and power gains losses really are. |
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Post by lemans1955 on Feb 3, 2015 17:15:24 GMT -6
I would love to see those results, I am specially interested in the stock 73 exhaust vs the stock 72 rams horn exhaust. About all most people can give me is that they sound better and "seem" to wake up the 73. As a racer who uses the stock suitcase exhaust but runs in an stock mod class where mild modifications are allowed this really peaks my interest.
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Post by dacota25d on Feb 3, 2015 17:54:23 GMT -6
Haha throw it on there and say that's how it came
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