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Rebuilding a 2 stroke?
- Thread starter unL33T
- Start date
Pro 6 sent out the piston and cylinder like 2 weeks ago back to CV Tech. I haven't heard anything in at least a week.
boyoboy
Well-known member
when you originally sent the cylinder to cv tech they should of insisted you included a piston to fit. anyhow, looks to be getting done now.
it has been mentioned that you had the compression ratio lowered during your last rebuild. It is likely that a thicker base gasket was used to lower the compression ratio. You might want to get an oem base gasket or other base gasket of oem thickness when putting the engine together. changing the base gasket thickness alters both port timing and squish. i would suggest you go back to oem when you have the engine put back together. you might want to source your oem gaskets (base and head) now to avoid any future delays.
edit: if you're engine has more than 20,000 kms I would suggest you change the crank seals.
it has been mentioned that you had the compression ratio lowered during your last rebuild. It is likely that a thicker base gasket was used to lower the compression ratio. You might want to get an oem base gasket or other base gasket of oem thickness when putting the engine together. changing the base gasket thickness alters both port timing and squish. i would suggest you go back to oem when you have the engine put back together. you might want to source your oem gaskets (base and head) now to avoid any future delays.
edit: if you're engine has more than 20,000 kms I would suggest you change the crank seals.
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gammaguy21
Well-known member
Didn't see this until after I sent you a PM. I have pictures of my bikes in the "post pic" thread... I don't want to go off topic here.
Engine has 14000 km on it.
Got a call from Pro6. They finally got all the parts back so they are starting to work on it. However, they found some things that bothered them.
1. These pistons have a black coating on them. They said one side of the piston had it completely worn off while the other side was only about 2/3 worn. They said that was strange.
2. They found tons of oil in the air box. As if someone had poured a quart of 2 stroke oil into the air box. I did re-oil my filter for the first time following the instructions on the K&N filter cleaner/oiler kit I have at home before it had it's major failure (thought maybe the air filter was dirty and that's why it was behaving a bit funny before it died). They said it was so bad that even if I had done it very poorly, it wouldn't look like that. Dunno.
3. They said there was lots of clear fluid, which they think is transmission oil, in the crank. I did change the transmission oil shortly before this all happened. I suppose it's possible I over filled it but I put in the amount specified in the manual, which is also stamped right on the casing. I had a feeling maybe I should've removed the clutch adjustment port, which would allow excess oil to drain, after doing the change. Although that oil wasn't clear... it looked like normal motor oil to me.
4. They said the bottom of the piston was extremely black including the wrist pin that came out indicating it was running very hot.
5. The head is damaged and either needs to be resurfaced or replaced.
They now want me to come take a look at it before they start putting it back together. I'm out of town tonight and will return tomorrow afternoon but it will be quite out of my way to get there tomorrow evening. So if I don't make it there tomorrow I'll stop in after work on Thursday.
Got a call from Pro6. They finally got all the parts back so they are starting to work on it. However, they found some things that bothered them.
1. These pistons have a black coating on them. They said one side of the piston had it completely worn off while the other side was only about 2/3 worn. They said that was strange.
2. They found tons of oil in the air box. As if someone had poured a quart of 2 stroke oil into the air box. I did re-oil my filter for the first time following the instructions on the K&N filter cleaner/oiler kit I have at home before it had it's major failure (thought maybe the air filter was dirty and that's why it was behaving a bit funny before it died). They said it was so bad that even if I had done it very poorly, it wouldn't look like that. Dunno.
3. They said there was lots of clear fluid, which they think is transmission oil, in the crank. I did change the transmission oil shortly before this all happened. I suppose it's possible I over filled it but I put in the amount specified in the manual, which is also stamped right on the casing. I had a feeling maybe I should've removed the clutch adjustment port, which would allow excess oil to drain, after doing the change. Although that oil wasn't clear... it looked like normal motor oil to me.
4. They said the bottom of the piston was extremely black including the wrist pin that came out indicating it was running very hot.
5. The head is damaged and either needs to be resurfaced or replaced.
They now want me to come take a look at it before they start putting it back together. I'm out of town tonight and will return tomorrow afternoon but it will be quite out of my way to get there tomorrow evening. So if I don't make it there tomorrow I'll stop in after work on Thursday.
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boyoboy
Well-known member
dang.
what kind of damage does the head have?
and did you not have a new piston sent to cv tech. what they are describing sounds like a used piston.?
when you put the engine back in after the last rebuild did you set the oil injection to spec?
clear oil on the crank and oil in the air box? what is pro6's take on that? maybe the tranny oil leaked/breached into the crankcase? would also help to explain the oil in breather? careful inspection might reveal. what is pro6's thinking?
I'm not sure I would correlate black with heat. blued metal, yes i've seen that.
dunno what to say or think. ask pro6 what they think. they need to come up with some thoughts on this. dang.
edit: bring donuts and beg pro6 to give sandy a call for his thoughts/maybe a look see?
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I haven't seen it but they said the head has some damage from the bits of piston and piston rings that were bouncing around in there.
I was describing the piston that was in it. I guess they thought the uneven wear was odd.
They seem to have no idea what's up with the oil in the air box or clear fluid in the crank case. They asked if I had the crank rebuilt last time as maybe the cases weren't sealed properly on reassembly but we didn't do the crank last time.
They're going to look into it more I guess? They want to make sure it's not going to die again so fast.
I'm not entirely sure why they are so insistent I come look at it as I won't be able to contribute at all but I did ask them to either take pics or let me come take pics so maybe that's it.
boyoboy
Well-known member
old piston, of course duh my bad. i've been thinking about this and edited my previous post. for some reason im thinking the tranny oil may have breached the crankcase? it would also explain the oil in the airbox. after you changed the tranny oil how many km's later did the problems start?
Problems had already started but it died 2 days later.
I was also thinking about this and a few years ago (basically when I got it) it kept getting stuck in high idle and a leak down test was suggested but then I heard it was fairly normal for this bike and just ignored it. I set the idle lower and then it would drop back down so I just forgot about it but maybe that was a bigger issue than it was made out to be.
They said the oil in the air box was the same color as 2 stroke oil (red) instead of the clear stuff they found lower.
boyoboy
Well-known member
im stumped. maybe dellboy will know, or go on some of his two stroke forum sites to pick the brains of 2 stroke guru's.
Pics.
One thing I didn't get a pic of is on the top of the piston rod there was a visible ring scuffed into the inside where the bearing sits. They want to do the crank now because they don't know what's up with that and don't know the history of the bike and want to cover all their bases. Waiting for a quote on that before I say to proceed. At the least we'll do the crank seals.
Got this pic but it's not really visible.
One thing I didn't get a pic of is on the top of the piston rod there was a visible ring scuffed into the inside where the bearing sits. They want to do the crank now because they don't know what's up with that and don't know the history of the bike and want to cover all their bases. Waiting for a quote on that before I say to proceed. At the least we'll do the crank seals.
Got this pic but it's not really visible.
They want to replace it based on that wear inside the small end of the piston rod, regardless. I'm not sure if it's worth doing. A whole new crank is $650. The rod kit alone is $450. They said it's cheaper to replace the crank than do the rod kit.
It's a lot of money so I'm not sure what to do. I feel like I should let them do it as they are recommending, though.
boyoboy
Well-known member
Yes. I hear you. would be worth asking pro6 to save the old crank for you. lot of dough just for the connecting rod. I'm assuming the new crank comes with the rod for $650? Almost seems a reasonable price. I still think the crankcase was breached somewhere, hopefully they will closely inspect any seal (you mentioned replacing crank seals) or drive bearing / trans / seal? for damage that would allow the crankcase to leak.
edit: Asking them to carefully inspect all possible places the crankcase could have been breached wouldn't hurt. I would ask for a leakdown (pressure) test of both the 1. crankcase, and 2. the transmission after the rebuild. Tell them you want to be present for both tests. Mentioning this may motivate pro6 to take extra care when rebuildng your motor. Expected numbers/time are in the following article for both the crankcase and tranny.
good read here in plain english, the section on where to find air leaks is interesting http://www.klemmvintage.com/airleaks.htm
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I mentioned doing a leak down test to them already and they said they were already planning on doing it.
Yes, I will ask them to hold onto the old crank.
OMG!!! That's very expensive!!! They probably send it out.
http://www.pjme.co.uk/acatalog/Aprilia_RS125_Engine_Bottom_End_.html
PJME have Long brand rod kits for around $100 after the conversion. They make a lot of the OEM rods for Japanese manufacturers and I Used them in a little RD350LC race bike for years with out a failure. People who use them in race RD's and RZ seem to really like them. The also have Wossner - which I have never tried - and I'm sure you could get Prox for around the same price which I have tried and liked.
I can't remember the exact figure but the last single cylinder crank I had rebuilt was for my son's RM and it was about $100.
Could you just order the rod from PJME - they ship cheaply and quickly - and take the crank to Willy at WASP or Vance at Oshawa Precision?
Pro6 desperately need to go and hire Sandy back
Pics.
Does the head still have this damage? That definitely needs to be fixed as well.
You can buy an OEM or aftermarket for not too much money - http://www.pjme.co.uk/acatalog/Aprilia_RS125_Engine_Top_End_.html
Vance at Oshawa precision may also be able to machine and deck that depending on how much material is left and it would be a good opportunity to recut the squish band but you would need to have the cylinder and piston back on so you could measure
Pro6 says they are going to clean it up.
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