Author Topic: Will this work? (Read 6019 times)

lauterbacher · « **on:** December 15, 2012, 07:01:17 PM »

I have a vintage 125 Can Am, And litterally there are no oversize pistons available from anyone. Can Am used a 18mm wrist pin on there 125 bike after there first year. I can use a modern piston such as a YZ 125 with a 15mm wrist pin if I make a 3mm steel bushing to take up the space of the 18mm wrist pin. Oh and I have checked and there is no such wrist pin bearing made that would take up the space. Question do you think this would hold up? I could probably send it off to a person who does crank work and have a 15 mm top end rod put on but at some point I have to say enough of trying to keep this motor going. Thanks

2T Institute · « **Reply #1 on:** December 15, 2012, 08:00:59 PM »

NO bodges just swap the rod, the needle roller bearing needs to run on a hardened surface you bush would last a matter of minutes.

TMKIWI · « **Reply #2 on:** December 16, 2012, 04:56:11 AM »

Quote from: 2T Institute on December 16, 2012, 04:00:59 AM

NO bodges just swap the rod, the needle roller bearing needs to run on a hardened surface you bush would last a matter of minutes.

x2

Check what rods are available with your crankpin size and a 15mm small end.
Even if the length is longer you can raise the cylinder to suit.
Is the piston crown to wrist pin dimension the same with the YZ as the Can am ?

2T Institute · « **Reply #3 on:** December 16, 2012, 10:09:22 AM »

Can Am is beautiful engine and any time you want to sell it let me know. They have a 22mm crank pin 110mm length so a RM 125 post 05 or KTM 125. Piston IIRC has a 22mm comp height so just about ANY 125mx piston will be fine, depending on your bore size.

VintageBlueSmoke · « **Reply #4 on:** December 16, 2012, 11:51:21 AM »

Quote from: 2T Institute on December 16, 2012, 06:09:22 PM

Can Am is beautiful engine and any time you want to sell it let me know. They have a 22mm crank pin 110mm length so a RM 125 post 05 or KTM 125. Piston IIRC has a 22mm comp height so just about ANY 125mx piston will be fine, depending on your bore size.

Being a Can-Am guy...

X2

2T Institute · « **Reply #5 on:** December 16, 2012, 12:39:49 PM »

Can-Am is a brand the engine is pure Rotax.

SachsGS · « **Reply #6 on:** December 16, 2012, 03:06:16 PM »

Rotax (was a division of Fichtel & Sachs) is now a division of Bombardier.

I have 2 Can Am (Rotax

) disc valve engines. I'll see if an old Sachs 1251/ piston is compatible.

SachsGS · « **Reply #7 on:** December 17, 2012, 12:47:56 AM »

Sachs 15mm.

SachsGS · « **Reply #8 on:** December 17, 2012, 01:08:24 AM »

2T might skin me alive for this but could a guy bore/ream the piston from 15mm to 18mm and use buttons to locate the wrist pin? I've seen this sometimes in older Rotax sled engines.

lauterbacher · « **Reply #9 on:** December 17, 2012, 02:52:45 AM »

Is the 110 rod length measured ctr to ctr of the rod ends?

Helmut Clasen · « **Reply #10 on:** December 17, 2012, 06:38:11 PM »

Quote from: lauterbacher on December 17, 2012, 10:52:45 AM

Is the 110 rod length measured ctr to ctr of the rod ends?

I had great luck when I send my Con.rod problems on our SACHS engines to the company : CVTech in Thetford Mines Quebec.
www.CVTech-AAB.com
I think they can do anything and everything on any engine.
Great in NICASIL plating too....
They deal with WOESSNER piston Germany .

2T Institute · « **Reply #11 on:** December 17, 2012, 08:39:56 PM »

Quote from: SachsGS on December 17, 2012, 09:08:24 AM

2T might skin me alive for this but could a guy bore/ream the piston from 15mm to 18mm and use buttons to locate the wrist pin? I've seen this sometimes in older Rotax sled engines.

How do you put the circlip grooves back in?

Jeram · « **Reply #12 on:** December 17, 2012, 11:25:28 PM »

the teflon buttons are common in four stroke drag bikes, but the worry with them is what is stopping the bottons from moving and catching on one of the ports?

that is a big danger.

for around 250-300 bucks you can just get a custom piston made, Id imagine this is the cheapest option as once you pay 150 for a new piston plus 200 for the modifications you will be out of pocket

SachsGS · « **Reply #13 on:** December 18, 2012, 03:38:06 PM »

If a new rod is put in the motor (30+ year old motor, probably needs it) a guy should make sure the ring locating pin (s) on the new piston won't snag on a port.

In the case of the wrist pin buttons one should check if the wrist pin rises enough to interfere with the transfer port. I pulled apart a used sled of mine once only to discover that at one point in the sled's life the wrist pin had somehow walked over and scarred the cylinder wall. While the damage was ugly, because it was below the level of the transfer port it didn't affect compression.

A guy could sleeve the rod small end. A steel sleeve with a plated i.d. would work I think. One would have to calculate the tolerances for the bearing o.d., light press fit and plating thickness but if a guy didn't want to split the cases it could be done. A lot of the earlier 2Ts just had a bronze bushing for the small end.

lauterbacher · « **Reply #14 on:** December 19, 2012, 07:53:58 PM »

I was going to go with the boring out of the piston and the plastic retainers but it won't work with my port setup. I'm still thinking of trying a bushing and having it made of 0-1 heattreatable tooling steel. I am getting the machining for the bushing for free and I will do the heattreating my self. A $900.00 dollar vintage bike is not worth a new rod and a total of about $300.00 dollars for crank work. This vintage thing can get old fast.

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Author Topic: Will this work? (Read 6019 times)