Crankshaft question

G

goodman24x

Member
May 2, 2010
473
9
54
West Central Florida
I tried searching but gave up. I am going to rebuild one of my airsals. It currently has a vitos crank in it. It broke a piston skirt so likely have to renikasil the cylinder. However I will be splitting cases to do all new seals and check the crank.
I have no complaints with vitos but I keep hearing hot rods.
I can not find a good pic of the hot rods.
Can anyone tell me if it is a full circle like the vitos or is it cut out like the stocker. I know the vitos uses stuffer blocks which is lighter though.
Could someone post a pic of a stock stroke hot rod crank?
I will be doing full top and bottom including clutch.
Thanks for any help.
 
Can you tell me if they are full circle or lobes cutout like a stocker?
I want my cases stuffed with no open air volume.


If you had your choice which would you use and why? <<<-----open question to all builders
 
The lobes are cut out like a stocker. They look exactly like a stock crank except the pin hole is 2mm farther out towards the edge.

I like the Vito's +3mm stroker for everything except the most hardcore racing (hillclimbing, drag racing) because of the lack of trenching to the case. The 1mm stroke difference between the +3mm and +4mm stroker isn't going to translate into a certain amount of power.... once you get the +3 mm stroke, you get the piston below the transfers at BDC and you get the increased port timing.

The cases have two very thin spots (between the crank throw and input shaft and balancer shaft) and the trenching process leaves them with even less material. Just the tiniest bit of FOD injestion will break one of those two spots out.
 
I appreciate the info. Funny thing I emailed Hot Rods and someone emailed me back saying the crank was a full circle crank. I even asked if the lobes were cut out like the stocker8-|
I used to buy full circle cranks for my mini quad motors.
 
I think the Vito's is the only off the shelf crank With blocks. I would just make sure that it is within spec, including runout and put it back in
 
As long as the piston was forged, there *shouldn't* be any material in the bearings. Can't hurt to replace them though.
 
What's up Goodman? Nice season for you and the boy! Congrats! The 4 mill is not a full circle crank. If you're worried about the case volume, machine the crank webs to accept a couple of aluminum stuffer blocks and send it to Falicon for some balancing. If the skirt broke off the piston, we both know what you need to do.
 
OConnor Racing said:
What's up Goodman? Nice season for you and the boy! Congrats! The 4 mill is not a full circle crank. If you're worried about the case volume, machine the crank webs to accept a couple of aluminum stuffer blocks and send it to Falicon for some balancing. If the skirt broke off the piston, we both know what you need to do.
Click to expand...

Hey Ken, thanks!
Your confidence in me is flattering. I believe the cylinder is ready for a renikasil job. It had 10 races on it and a couple all day practices.:-[


I will probably stick with the vitos crank.

Can you explain to me what a "long rod" motor is?
I can not go over 200cc.
 
As Brandoz28 said, the only off the shelf crank with the stuffers is the vito's

A long rod crankshaft is a given stroke crank( stock, +3 or +4) with a 115mm long rod pressed onto it instead of the standard 110mm long rod. The longer rod decreases thrust forces on the piston and decreases the rod angle for a given stroke.

Unfortunately, this comes at a price. You must space the cylinder up 5mm to account for the increase in rod length. That's going to increase your crankcase volume..... whether the offset is worth it or not, I can't tell you.
 
Well, most all 2 strokes have full circle cranks, true.

Unlike the one pictured and most "high strung" 2 strokes (YZ, CR, LT, RM) the blaster cranks have a bit of counter balance built in in that the area around the rod bearing is "cut out" or more aptly described, not cast in. That reduces the amount of counter balance needed to get a well balanced engine because it helps to offset rod weight (somewhat).

All of the hot rods cranks (stock stroke or +4 stroker) I've seen are not full circle cranks. They look just like the factory cranks with the areas around the rod end not cast in. The vito's cranks are the only available (that I know of) off the shelf that have the stuffer blocks.

If you did go Ken's route (custom machined crank with aluminum stuffer blocks and dynamically balanced by falicon) you'd have a basically bulletproof crank (except for possible big end bearing damage from a blown piston again) but it would also be ridiculously expensive. For a racebike it might be worth it but that really has to be determined by your wallet.
 
So from what I am trying to understand:
The longer rod does not increase CC's because you actually lift the cylinder to compensate for a longer stroke?:-/
We can not go over 200cc

Ken,
I know Jordans blaster was fast as heck but he also had the CT motor and no one else had one at that time they were all airsals. We will be going against a CT motor this season. We holeshot it every time but on the big end he gets us. I did put a right bend pipe on to see if we can capture some top end but I am afraid it will hurt our holeshot.
Ken check pms
 
The long rod motor does not affect displacement because the big end bearing is travelling the same circumference (resulting in the same stroke). The advantage is a small bit of torque and longer piston/bore life.

If you are absolutely limited to 200cc's then a long rod is your only choice IF you want to go with a difference setup other than a stock crankshaft (or the vito's stock stroke crank to get the stuffer blocks).
 
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