Rebuilding a 2 stroke? | Page 10 | GTAMotorcycle.com

Rebuilding a 2 stroke?

unL33T said:
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.
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That coating on the piston helps with breakin and wears off fairly easy. It should all be there on a new piston. Do you have a picture?

The oil in the air box is really strange. I know some bikes vent the crankcase into the air box. I guess the theory is that it get burnt in the engine although I'm not sure is that is more ecologically sound that just letting it drip on the road. Does it look like 2 stroke oil. Half a bottle sounds like a lot. Is there a little drain tube for the air box with a plug in it?

Possibly there was too much oil in it causing the air box problem but you seem to have filled it with the right amount. Strange.

The only other thing I could thing off for the clear fluid in the crank is gas. I don't know what kind of petcock they have but I've had problems with the vacuum one on the RZ where they get stuck open and if your needle valve is not seating right gas continues to run into the carbs and then into the cylinder where it evaporates and leaves a thick liquid behind. Do you know if it smelt like gas? Maybe with it sitting the crankcase was filling up.
 
unL33T said:
Pro6 says they are going to clean it up.
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Perfect. Dings like that can cause hot spots and overheating. Did this happen this time or the time before. If it was before and it was put back on like that it would not have helped the overheating they mentioned.
 
Delboy said:
Perfect. Dings like that can cause hot spots and overheating. Did this happen this time or the time before. If it was before and it was put back on like that it would not have helped the overheating they mentioned.
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I think it happened this time.
 
UnL33T. Any news? Are you back on the road yet? I saw a RS125 today and was thinking about this thread
 
Still at Pro6. The crank took over a month to come from Italy but they were supposed to get it yesterday.

Otherwise no updates.
 
Crank arrived last week. Gasket kit was wrong item.
 
They called me and let me know bike is put back together and heat cycled a few times but they suspect the pilot jet may be clogged which could have caused the problem to begin with. They wanted to clean the carb. I told them to go ahead with that and to also check that the jetting is set properly as I have no idea what the previous owner had done there. They said it should be done by the end of the day.
 
I don't think this bike has a fuel filter. Perhaps I should have them add one. I actually have one at home that was in the box of parts the previous owner had.

Looks like this:
7MM-FUEL-FILTER.jpg
 
Nothing wrong with having a fuel filter, it's cheap insurance. But a clogged pilot jet is usually due to fuel evaporating during storage. The dissolved solids and waxes won't be caught by a fuel filter.
 
Bike is done. Repair cost after tax is $3345.70. This doesn't include the fact that I paid about $400 to repair the cylinder before this.

So basically a bit more than the bike is even worth. Fun times.

15.5 hours of labour is included in there.

Pilot jet was plugged solid they said.
 
unL33T said:
Bike is done. Repair cost after tax is $3345.70. This doesn't include the fact that I paid about $400 to repair the cylinder before this.

So basically a bit more than the bike is even worth. Fun times.

15.5 hours of labour is included in there.

Pilot jet was plugged solid they said.
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Considering the length of time it was in the shop and the problems encountered, 15.5 hours of labour seems low. Glad to hear it's back on the road again.
 
unL33T said:
Bike is done. Repair cost after tax is $3345.70. This doesn't include the fact that I paid about $400 to repair the cylinder before this.

So basically a bit more than the bike is even worth. Fun times.

15.5 hours of labour is included in there.

Pilot jet was plugged solid they said.
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Glad to hear the mystery is solved. Unfortunate you had bad luck with it previously.
 
Brian P said:
Nothing wrong with having a fuel filter, it's cheap insurance. But a clogged pilot jet is usually due to fuel evaporating during storage. The dissolved solids and waxes won't be caught by a fuel filter.
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Will adding fuel stabilizer help? I tend to use a decent amount of SeaFoam in it as I hoped that would help prevent build up in the carb but I'm probably mistaken about that. Is there some other additive that could help prevent it? I think I had one year I stored it without any kind of stabilizer in the fuel.
dricked said:
Maybe a good reason to make sure to use ethanol free fuel if you weren't.
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Does fuel with ethanol plug carbs faster? I try to get ethanol free fuel when it's available but if it makes that much difference I can be more religious about it.
 
It does in vehicles that sit. It could have happened over the winter but to be safe I would use it as much as possible. For the few extra dollars it'll cost over the life of the bike it's cheap insurance. I'm assuming the bike is easy to work on so maybe a spring carb cleaning would also be a good idea. It's very easy and takes just a few minutes after the carb is on the bench
 
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dricked said:
It does in vehicles that sit. It could have happened over the winter but to be safe I would use it as much as possible. For the few extra dollars it'll cost over the life of the bike it's cheap insurance. I'm assuming the bike is easy to work on so maybe a spring carb cleaning would also be a good idea. It's very easy and takes just a few minutes after the carb is on the bench
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I don't have any other 2 strokes to compare to but I'm pretty sure I've been told this one is not all that easy to work on, lol. They definitely told me this is one of the hardest and most precise rebuilds they've done. They were very happy I found a copy of the service manual to send them.

While Pro6 had it they were telling me a connecting rod kit of this bike is over $400 so it made more sense to buy the whole crank assembly for $650 but now I'm finding connecting rod kits for around $100. Makes sense to get one to rebuild the old crank as a spare?
 
CV Tech also charged Pro6 to rehone the cylinder after telling me it would be free. They have such terrible customer service.
 
unL33T said:
I don't have any other 2 strokes to compare to but I'm pretty sure I've been told this one is not all that easy to work on, lol. They definitely told me this is one of the hardest and most precise rebuilds they've done. They were very happy I found a copy of the service manual to send them.

While Pro6 had it they were telling me a connecting rod kit of this bike is over $400 so it made more sense to buy the whole crank assembly for $650 but now I'm finding connecting rod kits for around $100. Makes sense to get one to rebuild the old crank as a spare?
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For a full rebuild, absolutely! To pull the carb and float bowl off to pull the jets there's no precision and it's very straight forward being a single cylinder/single carb.
 
Picked up the box of damaged parts today. There must've been some communication failure somewhere because there was no odd wear on the small end of the connecting rod like they told me. They had previously said there was a shiny ring worn into the end but you couldn't feel it with a fingernail but in reality it on on one of the other bigger surfaces of the crank and definitely visible and could be felt with a fingernail and there was more than one spot.

They recommended against installing an inline fuel filter as it may disrupt fuel flow since there is no fuel pump either and they were worried the filter may disrupt the gravity feed enough to starve the fuel and cause it to run lean again.

They suggested that rather than store with stabilizer for the winter that I should drain the tank and carb for storage to prevent this problem in the future.
 
A fuel filter is a GOOD idea. If it is sized correctly you WILL NOT have feed problems. (If you still worry about feed, put a larger diameter clear fuel line on AFTER the filter. That will act like a reservoir). All my bikes are gravity feed fuel systems, they all have filters and fuel starvation because of the filter has never been a problem.

Draining the tank and carb is a GOOD idea. If you installed that "dry break" in your fuel line use that to drain the tank. To drain the carb loosen the screw on the bottom of the float bowl and drain it into a small bowl (I use the lid of a spray can). The screw is easily reached with a long straight screw driver.
The jets in that thing are so small I would drain the carbs if it was going to sit more than a week or two.

This time BE SURE to get the head and barrel " re torqued" after you put a couple of heat cycles into that motor.
 
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