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Workshop => Engine and Bottom End => Topic started by: havinnoj on November 05, 2018, 11:54:23 PM

Title: 363 370 Vibration
Post by: havinnoj on November 05, 2018, 11:54:23 PM
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.
Title: Re: 363 370 Vibration
Post by: broken1 on November 06, 2018, 02:51:37 AM
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.  ;)
Title: Re: 363 370 Vibration
Post by: Skeans1 on November 06, 2018, 06:16:01 AM
From what I remember of my Sphinx the vibrations weren’t all that bad nothing like the 431 was.
Title: Re: 363 370 Vibration
Post by: jwraymond6 on November 06, 2018, 07:26:13 AM
I don’t notice much vibration on my 363 sphynx
Title: Re: 363 370 Vibration
Post by: atvcrazy on November 06, 2018, 09:00:57 AM
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
Title: Re: 363 370 Vibration
Post by: Burns363R on November 06, 2018, 12:14:01 PM
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.
Title: Re: 363 370 Vibration
Post by: havinnoj on November 06, 2018, 12:50:41 PM
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. 
Title: Re: 363 370 Vibration
Post by: havinnoj on January 08, 2019, 04:45:44 PM
Motor is finally out of the chassis and in for inspection.. also found a cracked motor mount on the stock chassis.
Title: Re: 363 370 Vibration
Post by: Burns363R on January 10, 2019, 11:47:28 AM
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.
Title: Re: 363 370 Vibration
Post by: havinnoj on January 10, 2019, 02:26:04 PM
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.
Title: Re: 363 370 Vibration
Post by: havinnoj on January 10, 2019, 03:57:07 PM
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.
Title: Re: 363 370 Vibration
Post by: Tbone07 on January 30, 2019, 10:58:30 AM
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
Title: Re: 363 370 Vibration
Post by: 2Nubs on January 30, 2019, 12:14:26 PM
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.