Rebuilding a 2 stroke? | Page 7 | GTAMotorcycle.com

Rebuilding a 2 stroke?

bitzz said:
Regular type calipers won't work. You need, ideally, a bore gauge... I don't have a bore gauge either, so I use a telescoping gauge kit.

You need to measure the bore one third ,then two thirds from the top, measuring twice at 90 degree angles at each step.

Do you have a piston?
What you're REALLY interested in is the piston to bore clearance.
Put the piston in the bore about half way down and ram feeler gauges down in there beside the piston. The biggest one (decided by two) is your piston to wall clearance. (Move the piston up and down to be sure it is the same everywhere).

If you want it is very simple to get that thing some more compression. Bring it up and we'll swap the base gasket... and I could measure that bore for you.
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Don't have a piston. They are sold in several slightly different sizes so I figured I'd measure first and order the closest size. I'd appreciate the bore measurement.

Not overly concerned about the low compression as long as it runs nice. Do you have the left over base gaskets? I don't seem to have them in any of my parts boxes at home. Wouldn't be the first time I accidentally threw some good parts out while cleaning up (just the other day I threw out part of a PC case I needed thinking it was just a chunk of scrap metal, DOH!).

Riding to work on Friday it seemed just a touch low on power but I didn't really pay attention to it. On the way home it seemed much lower. Seems to have lost all the "punch" at higher RPM and it doesn't want to redline in first anymore. Stalled on the road at one point. Seems to sputter a bit when I first get on the throttle sometimes. I changed the transmission fluid on Thursday but I can't see how that would affect it unless maybe I over filled it but I put in 600cc as per the specs. Seemed to be running a bit hot lately, too, but it was only a problem when stuck in traffic. Came within 1 bar of the highest on the gauge at one point.

Over the weekend I cleaned the air filter for the first time and finally got around to checking the setting on the oil pump. Air filter was barely dirty and is surprisingly annoying to get in and out and took forever to dry between cleaning and oiling. Had to drop the oil tank in the back to get to the rear air filter bolts. Luckily it's only held in with 3 screws (and 1 was missing, lol). Oil pump was set way too high so I lowered it. Dumped a can of SeaFoam into the tank to help clean out any junk but I have no idea if that ever makes any difference. Took a look at the spark plug and it was looking pretty grimy but I didn't replace it yet. Might grab a replacement on the way home if it's carried by PartSource/Canadian Tire. Took it for a test ride Saturday night and again it stalled at one point.

Rode it to work today (avoiding the highway). Still didn't want to rev up at first but seemed a bit better by the end of the ride but still down on power. Will double check compression today if I can (should've done it on the weekend, not sure why I didn't) and maybe try changing the plug. I still haven't changed the power valve, which you mentioned to me looked like it was wearing and needed replacement (plus it had a gouge in it from when the rings blew up) so maybe it's an issue with that? I have the replacement valve and seals but I don't have a new gasket or spring. Not sure if I need them. Power valve is tucked behind the radiator so might be hard to replace without dropping the rad, which I'd rather not do.

I thought maybe it was a clogged air or fuel filter but the air filter seemed fine and cleaning it made no difference and I can't find a fuel filter on this thing or in the parts list so I don't think it has one. Only thing it has is some kind of vacuum valve on the base of the tank. No idea how that works or what it does but it seems to still be connected properly. There's a large air bubble in the fuel line I couldn't get out but I think that's been there for awhile and didn't seem to ever hurt anything before.
 
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Change the plug before digging into anything else. If yours is fouled a new one will make a huge difference. The recent hot, humid weather will make you run richer and contribute to fouling the plug faster.

Edit: as a convenience, consider buying a second air filter. Oil it now, let it dry, then stick it in a big zip lock. Label the bag so that you remember that it has been oiled and is ready to go. Then you can just swap it over next time without having to wait
 
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Ash said:
Change the plug before digging into anything else. If yours is fouled a new one will make a huge difference. The recent hot, humid weather will make you run richer and contribute to fouling the plug faster.
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Will do! Thanks!
 
Stopped at PartSource and they don't have the part in stock or in their warehouse. Dumped another can of cleaner through it with no affect except lots of smoke (that got some funny looks from the soccer fans celebrating along St. Clair West lol). I didn't expect it to do anything anyway.

Found a new plug in my boxes of stuff at home. Checked compression, it's down to about 75 PSI already. Changed the plug and it had no affect on the performance. In fact, after the plug change the bike would almost die when I just started to crack the throttle. But I figured that was from left over fuel/oil from turning the engine to check the compression. Then it died again in traffic awhile later. Got a fresh tank of gas and that seemed to help but could be my imagination and I didn't go far from the gas station (just home).

Also seem to have something going on with the starter button and/or kill switch. Got nothing from it when I was trying to leave work but then after fiddling with both for awhile it started. Guess there's something else to pull open and check out. I know the horn wires got disconnected from the switch a couple years ago from stress on the cables and I had to resolder it so maybe something similar is going on in the controls on the other side. Horn still works! Will have to check it out later. Guess it might be related but I'm assuming probably not.

Will report back after my next longer ride.
 
Opened up the starter/kill switch assembly and it looks fine. I did start to wonder if it is actually related after all, though, because the few times it's stalled in traffic the starter button was non-responsive as well which left me stuck in the middle of the road and I had to move over and try it a couple times. Hmm. We'll see on the next ride, I guess.
 
boyoboy said:
can't wait for delboy to chime in here, 2 stroke bikes are his "thing" and he has lived with an assortment of the critters. delboy?
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He did some stuff for me in the past but I think his company moved him to the US. I don't think he checks in a lot.

I live in the east end and he recommended Willy at WASP in Ajax or Vance at Oshawa Precision for RZ work. I also don't think you can go wrong with Gord Bush as boyoboy said. I also think the other half of that team, frank Leitner, is or was at Steffan Engineering in Oshawa.

I had Sandy at Pro 6 set up my RZ on the Dyno after it was built. He did a great job.
 
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Still has a problem. Rides like it peaks out at 6k RPM although it will rev higher but doesn't have the power it should at the higher RPM. I'm leaning towards stuck power valve? Maybe I should just let one of the experts mentioned here take a look at it.
 
Well she just died on Eglinton. Currently at Eglinton and Martin Grove waiting for CAA if anyone wants to chat, lol.

Gonna tow it to Pro6.
 
Wtf. CAA won't be here until 5:15pm.
 
Sorry to hear about this. I think they are such a beautiful bike.

How many KM's since the rebuild?

I hope you get it sorted
 
Iceman said:
Joe Bass taught me this, @Delboy

Sent from my Le Pan TC802A using Tapatalk
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Obviously I didn't do a great job...you forgot the @ in front of my name ?

Sent from my custom purple Joe Bass mobile device using Tapatalk
 
j2 said:
Sorry to hear about this. I think they are such a beautiful bike.

How many KM's since the rebuild?

I hope you get it sorted
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About 2k I think. It's at Pro6 now. They told me Sandy isn't around much anymore but they have a newer guy that's into 2 strokes. Can't recall his name. Think it started with C.

They had an identical RS125 in the shop at the time.
 
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unL33T said:
About 2k I think. It's at Pro6 now. They told me Sandy isn't around much anymore but they have a newer guy that's into 2 strokes. Can't recall his name. Think it started with C.

They had an identical RS125 in the shop at the time.
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I think Sandy does the trackdays in the summer. Most of them are at Calabogie so I guess that's why he's not around much
 
Interesting but at this point I'm thinking a 4 stroke might be a more reliable choice for a 2nd bike lol.
 
Iceman said:
Please view this ad:

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Price: $*3,500

Download the application from the Google Play Store.
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I want that so bad.

Sent from my Le Pan TC802A using Tapatalk
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Mmmmmm..... That looks like a nice one, and the price is OK as I've seen people asking more than that for basically junk. The KR colours were always my favourite.

Not sure if its an original KR as I though their wheels were gold?
 
Quick update: Pro6 hasn't got to it yet. Not that I really expected them to.

Hmm... still no update from them today.
 
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Called Pro6. They said the piston is cracked in half and the cylinder is damaged.

Fun times.

Guess I'll be dropping off the replated cylinder tomorrow and they can source the piston and other parts. Guessing this is going to be expensive (again).

Hopefully I can get some pics of the damaged parts.
 
Just dropped off cylinder at Pro6. All they know at this point is something caused damage to the exhaust side of the piston. Could be same thing as last time, could be something else.
 
Hope it's just the top end - and nothing from the cracked piston or damaged cylinder made it to the bottom end.
You have the cylinder already, hopefully they can get a good size match with a piston and not have to do any more cylinder work.

You should post pics of the piston and damage in the cylinder... maybe some of the more knowledgeable two stroke guys can identify what happened.

Hope you get it sorted.
 
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