So, What do I have here?

Bob Vehring · Post by **Bob Vehring** » Thu May 07, 2009 7:17 am

Bought a '83 several months ago. Seller said he had new cyls and pistons installed but couldn't get it to run.. Looking threw the plug hole and ex port, this appeared to be true. Both sides pulled 150 psi. Cleaned carbs and got it to run, with in 3 min. idling I heard it start to loose power. Look up the ex. port and saw coroners of pistons starting to scuff.
When I pulled it apart it had scuffing on 4 corners. One side had 1 1/2 tho, the other 2 1/2 tho. piston to wall clearance, IMO to tight but not familial we these engines.
My understanding was these should be an alum bore with chrome plating, these have a cast iron sleeve. Did any years have that or is this someone else s work? The new pistons have a clover leaf design logo on them, is that OEM or some aftermarket I am not familure with? With a cast Iron sleeve, will these pistons work? Bob

Post by **Vmax540** » Thu May 07, 2009 2:34 pm

Bob,
Aftermarket Iron Sleeves are available and can be bored. What you have to do is use aftermarket piston rings designed for the Iron sleeves unlike the OEM Rings which are only for the OEM chrome bore. Wiesco sells both style of rings CD= sleeved/iron bore which come in stock bore size on up and CDM = Chrome bore rings which only come in the stock bore size.

Piston Skirt Clearance New/ Max 0.065~0.070mm/ 0.10mm
Ring End Gap Top/ 2nd 0.35~0.55mm/ 0.35~0.55mm
Ring Groove Clearance Top/ 2nd 0.35~0.55mm/ 0.35~0.55mm

OEM Piston 8U900 8U9-11631-01-94

Now I have these rings on my Inventory/Parts list Chrome bore R09-816 A.M. Kimpex in which Kimpex tells me they can be run in an iron bore...... I have used them on chrome bores with good luck but, have not tried them on iron sleeves so, I can not say.... ?

vmax-540 · Post by **vmax-540** » Thu May 07, 2009 8:05 pm

Are the scuff marks lined up with the studs? I have seen a lot of sleeves installed and if not done properly and the right clearance set this will happen .People forget that when the manufacturer set these clearances they do this with the intension that there are chrome plated aluminum cylinders not steal sleeves,aluminum expands more then steal so if and when you install steal sleeves you have to add a little more clearance to make up the difference for the steal sleeve not expanding as much as the aluminum plated cylinder. Any time I install a steal sleeve I always add about .002 more clearance,I would replace the pistons and have the cylinder re honed with the added clearance,(do not use a glaze breaker or ball hone ,take it to a machine shop and have it done on a GOOD cylinder hone)

Bob Vehring · Post by **Bob Vehring** » Thu May 07, 2009 9:08 pm

Thanks guys We have a sunnen hone, a mill, and lathe,ect but build small racing 4 strokes for a living, been quite a while since I've done big sled engines. Mostly I was wondering what came stock, I see now what I have didn't. Many years ago, when we raced I had a friend that raced these engines He was sleeving them and using bigger Ski doo pistons to bring this engine to around 600cc. More then just the bigger size, his feeling was the ex port was a bit to wide for 535, and did have a problem snagging the ring. I guess seeing how it allready has sleeves, I'll look into the same plan this summer. I'm not looking to race, won't be fastest across the lake around here. I do want something that will keep up with the newer sleds in the woods, more then anything I always like the looks of these sleds.
Not sure how sled pistons have changed over the years, nowdays we have pistons made just for our kart racing engines that have both a higher silicon content and are machined now so out of the box (cold) they are not round, but become round under operating temp meaning, areas with more mass, like the pin, area expand more when hot then other areas. There was a time when we had to run quite large clearances on them but now can get away running them very tight.
Just another off hand question, did anyone ever really weigh one of these sleds? I think, but its been awhile, my '81 SRV came in about 430 on our scales, I'm guessing these should be alittle more. Wished I weight mine before I took it apart

vmax-540 · Post by **vmax-540** » Fri May 08, 2009 5:32 am

Bob I don't think that you can bore those out to 600cc with the standard sleeves,they need to have 77mm pistons to bring them up to 600cc and the standard sleeves can only stand about 75 or 76.Call LA sleeve and thay can make you some oversize sleeves to do what you want.

Bob Vehring · Post by **Bob Vehring** » Fri May 08, 2009 8:11 am

I have dealt with LA sleeve before, good guys. I haven't measured the sleeve I have yet nor have I tracked down Perry to see exactly which piston he used.. Need to get past the opening of the kart season here first. Were supppose to be in Savannah Ga this weekend for a race, but, the first 4 weeks in a row here at our track have rained out, again it looks like rain tomorrow but were hoping Sun will be good here. Have to take care of business first, then I can get back to this.

I do appreciate the help getting me to understand this engine, so one more of my endless questions. Was the 535 the only engine of this design, or did it morf into other larger engines that came in later sleds

Post by **Vmax540** » Fri May 08, 2009 9:54 am

Bob, 600cc Skidoo pistons.....There have been guys on here looking for replacement pistons for the 600 kits a couple of aftermarket speed shops sold in the 80's and no one could tell them where to find them or even that they may have been a Skidoo piston. Any information you can find on this could be made a part of the Articles section !

I don't have Yamaha's listed dry weight in front of me but, if memory serves me..... it is around 462 Lbs ? The Exciter is simular in design but, as far as I know no parts will interchange.

B.T.W. Good luck Racing !

Bob Vehring · Post by **Bob Vehring** » Fri May 08, 2009 1:20 pm

I'm not sure which SD pistons he used, Haven't had a chance to find him yet, but I will.
I know ARIES, Wisco and J&E have made custom pistons for karting, not always cheap but its not really hard for them to make and they will do it. I just need time to tear a few things apart here and measure. I have some 617 SD's here, we'll see what they measure

vmax-540 · Post by **vmax-540** » Sat May 09, 2009 7:10 pm

Bob .. The 617 is a 76 mm bore but the wrist pin diameter is only 18mm and the Vmax is 20mm.The 81 SRX 440 engine is BASICLY the same as the Vmax but very few parts will interchange. The crank,cases,cylinders and heads are all different and it only has a 66 mm bore size ,very few others parts are the same also. I have been trying to find some pistons myself as I want to make a big bore 600 myself.I used to own a auto motive machine shop and I haven't been able to find any that will just drop in. The one engine I would like to get a piston for is the 600 small block Polaris as that has the same bore & stroke and also the same pin diameter,just not sure of the pin location or ring end gap location. If any one has a old piston for one of these engines please let me know as I would like to buy one. The Yamaha mechanics manual lists the 83 as 452 lbs dry,the 84 and up lists it as 472 lbs dry,I know that the 84's chassis was beefed up a little that may account for the added weight.

Bob Vehring · Post by **Bob Vehring** » Sun May 10, 2009 11:39 pm

Jeff, I haven't tried to sort out the numbers yet. Next week I'll take two of my 617's out to the track to compare porting timing notes on them with Steve Decker, he's the expert, not me, but after that I'll tear them apart and have the piston in hand, haven't looked yet but if pin size is the only problem, should be an easy fix.
Heres my next question on the V engine. Mine has an iron sleeve, unknown, at least by me, origin. Are these a straight walled sleeve or does it have a thicker lip at the top and the walls are thinner for the rest of the sleeve .
Having to bore thru it to find out kinda defeats the advantage of allready having it

vmax-540 · Post by **vmax-540** » Mon May 11, 2009 3:26 pm

Yes Bob they do have alip at the top, most sleeves were made by LA sleeve and I think but not sure that Advanced sleeve also make some. There was a off the wall sleeve maker that made some back in the 80's that made some real poor sleeves for them nothing lined up and were a odd size but I haven't seen them in a long time so I would quess that you have LA sleeves in there.