Let's talk stroker cranks, 4mm to be specific !!

[sandpuppi101]

Well here I go again,my brother ( Joedirt) here on the board's seem's to have something with these dang Banshee's.I 1st off ain't a big Yamaha fan and I really don't care for Banshee's 2nd.And the kicker of all of this Banshee stuff is that I alway's seem to be the one who's wrenching on the damn thing's too.Anyway's he just picked up this Banshee,it's an'87 and from what we're to understand it's got a new 4mm stroker in her.Instead of the older style plate to gain the 4mm at the base ,I am told it has a stroker crank with differant rod's.The person whom he got the machine from is a pretty good friend and attest that it does have the stroker kit.I think it's a Vito's set-up and this Banshee is supposed to be a rockett.Anyway's since I'm gonna be working on this machine,just wondering if any of ya's can hook me up with any info on these 4mm stroker crank's or any mod info at all.Here's a couple of pic's,obviously it has newer plastic's..Any clue what year,just for reference..Thanks Gang ...

[SYKO]

OOOO scary J-arm banshee!!!, cant help ya on the stroker deal just looking at the crazy J arms.

[Mosh]

I cant be sure of the exact year. It is defiantely a 87-90 frame.
But it has newer plastics and a later model seat on it.The older seats were lower.

As far the engine, look and see if there is a white rubber plug below the rear engine mount.That will tell you if it is a older engine.
The 87,88,89 engines were "Stronger runners" for some reason and I believe it to be true since Tammy's Shee has the 88 motor set-up identical to my 96 and hers would kill mine in a race. The early year engines had a rubber plug for a speedo provision from the old days, on the back of the engine block being from the 2 wheelers.

As far as the stroker, if there are no spacer plates, I would only guess that there are different pistons in it to work with the 4 mil crank.
I honestly dont recall a set-up like that.
Call Vito's they will help you with some info, or I am sure Ronnie knows the ins and outs of a set-up like that. He has a lot of Shee knowledge.

[zmpolaristech]

I have built quite a few banshee motors, and a couple have been the 4mil strokers. you can run a stroker kit without a spacer plate, but the head would have to be cut for the 2mm higher piston height at TDC. also, the cylinders SHOULD be ported if set-up like this, or it will throw your port timing way off. (it will run though, and have a killer bottom-end, but NO top-end). Also, the only "special rod" i have ever seen on a banshee crank is the 5mil long rod (whitch is pretty common on the stroker cranks) and this just requires a piston with a 5mm higher wrist pin, but this does nothing for the 4mil stroke. I have NEVER seen a banshee stroker kit that didn't require either a spacer plate, or stroker domes in the head, or a combination of special thick base and head gaskets. If you have any other questions, PM me, I have a LOT of experience with banshee's, and i have a few good aftermarket parts kicken 'round the garage.