TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: havinnoj on November 05, 2018, 11:54:23 PM
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Fellas running 363/ 370cc motors with unbalanced cranks, what's the vibration like? I can't remember back to the last 350 I had and am considering doing a 363 Sphynx for the spare duner over the winter. I probably wouldn't care for myself but usually have a gal riding that bike so vibration becomes a bit more of a concern. Probably won't go that route if I need to spend the extra coin to balance since that motor size is already getting big enough for the spare.
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I have no experience with vibrations in a big bore but the fact a chick will be riding a 363 sphynx is awesome! My wife gets a measly 250cc oem cylinder. ;)
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From what I remember of my Sphinx the vibrations weren’t all that bad nothing like the 431 was.
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I don’t notice much vibration on my 363 sphynx
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balancing helps very little in my opinion. Running a standard stroke crank will help the mos with a big bore. Small motors like 72 mm bore or less a 4 mil is fine. Once you go over that the more they vibrate. Standard stroke will be easier to start as well
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I havent had any issues. I run 2 hour races without problem. I would say its probably not at smooth as a OEM 250, but then again i cant remember the last time i rode one of those.
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Thanks guys, appreciate the feedback. Probably only one way to know for sure. It'd be replacing a 300/310PV which could probably use a new piston so I'm weighing whether to put money into that top end or go bigger.
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Motor is finally out of the chassis and in for inspection.. also found a cracked motor mount on the stock chassis.
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They do vibrate some. Defiantly noticeable when compared to a stock 250 cylinder. But i ride my 370 for 2 hour races, and it isnt bad. My 450 vibrates just as bad id say.
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They do vibrate some. Defiantly noticeable when compared to a stock 250 cylinder. But i ride my 370 for 2 hour races, and it isnt bad. My 450 vibrates just as bad id say.
Thanks Kyle, appreciate it.
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PRICE CHECK ----
What's a Pro-X Powervalve 310 cylinder worth used these days? Comes with fresh bore/hone and good piston ready to run.
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One of the things I'm surprised that nobody has come out with is a counter-balancer designed to be run on the big bores. There so many big bores out there, I bet they would sell like hotcakes for guys 350cc and up
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One of the things I'm surprised that nobody has come out with is a counter-balancer designed to be run on the big bores. There so many big bores out there, I bet they would sell like hotcakes for guys 350cc and up
Agreed. I had a KTM 690 a few years back. Properly counterbalanced. Smoothest running engine I've ever been on.