New Cylinder Prepping and Breaking In

[drawkward]

Okay, so I've got a few questions regarding new cylinders.

As for chamfering the ports... Can someone let me know in a little more detail how I should go about doing this? I don't want to ruin my new cylinder by not doing this step correctly.

I may or may not smooth out the exhaust port. I haven't decided yet. I have a dremel, but I'm kind of afraid of making things worse. How easy is it to mess up?

Breaking in... I've never done it. If I were to keep the oil injector system attached and running, how much oil should I add to my gasoline to get the right mix? Also, I read somewhere before about different throttle stages at different miles. My odometer is not accurate at all, so I'll be doing this by guessing the amount of time on the cylinder.

I've heard horror stories, so I'm trying to do everything exactly right to avoid any mishaps.

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Edit: (Chamfering) I Found this video. They make it look so easy... Is it really this simple to do?
www.youtube.com/watch?v=bFkpxW4xHhA

Edit: (Break-In) I've done about an hour's worth of reading on breaking in a cylinder. Comes down to two different methods. A) Slow and Easy and B) "Ride it like you stole it". Seems to me that both methods make a good point. I'm torn between the two. I've always heard of the slow and easy method, but damn, the ride it like you stole it method sounds so tempting! What did you guys end up doing?

[90GTVert]

Chamfering is simply rounding or beveling the edges of the ports slightly. It helps to reduce wear and tear on the piston rings. If you run your finger over the port and it feels sharp or catches your finger a little, it needs to be chamfered. That video does show how easy it is, although it is easier to avoid a slip that could gouge your cylinder walls if you just use small files. I picked up my little precision files from Harbor Freight cheap. More info on the precision files HERE. The exhaust port is pretty simple. Take your time and use a lower speed at first to get used to it. You don't necessarily want the exhaust to be larger, just not rough. Be careful when working near the cylinder walls so you don't damage them.

49ccscoot.proboards.com/index.cgi?action=display&board=yamajog&thread=354&page=1

I've never broke one in with anything but straight premix, but I believe others mix the oil in the gas tank at 50-100:1 when they are keeping the injector.

I always do a hard break in. Works for me so far. Just make sure you vary throttle positions on the first ride, don't just stay at one RPM all the time.

[2strokd]

I kinda do both on my break ins...I do a few heat cycles @ about 2,000rpm or higher(not normal idle yet), let it cool and check the bolts and check for leaks. Then if all is good i go up and down the street cycling the throttle with a few short full throttle bursts for a seat of the pants carb(jet) check.
If it acts weird or bogs out at any throttle position, take mental notes and go straight home for tuning(jetting) and check for leaks again. Leaks really arent that common, but they WILL destroy a good motor so check for em, their sneaky sometimes. I had a bad crank seal and ended up "over jetting" on the extreme rich side to compensate for the air leak without even knowing i had the leak until it was REAL bad. One of the first signs of an air leak for me was a funny or stumbling idle. If you get a bad idle that tuning wont iron out, you probably have an air leak. It should be checked ASAP!
If all feels well and the plug looks good after a few short rips up and down the street, then its BALLS TO THE WALLS for me! No problems yet...

[drawkward]

Haha, now I'm even more excited! Thanks guys for the invaluable information that can only come from experience.

So here is my plan. I'm going to electical tape the shit out of my intake, just in case. I'm also going to reapply some silicone to the top of the reed block to eliminate any possibilities. When it comes to the base of the cylinder - I'm going to just clean up the block really really well so that I can spot any moisture coming from a leak.

Sound like a good plan?

[2strokd]

Electrical tape wont work with oil or fuel.
As long as everything is clean and true you shouldnt have a problem.
Clean is good, real good on an air cooled engine. Cant cool itself with a
blanket of dirt and grease on it.
Before i made a leak tester i kept everything really clean so i could spot any leaks, good
idea. Also, like Brent mentioned, carb cleaner works good for a quick running check if you
ever suspect a leak.

[Greg]

I was paranoid doing my BBK because of Benny over at SD.
Benny122 had an Autoech BBK installed and he blew it up rather quickly.
I actually postponed my BBK install until I could see the post-mortem of his cylinder.

I have developed my own theory on what may have happened to Benny's kit. It looked pretty obvious that is was a seizure due to lack of oil.
He said he added extra oil to the tank while still using the oil injection.
My theory was that the current gas in his line did not have oil in it as the oil he added was still in the gas tank. It is also possible that since the carb was taken off for re-jetting that the oil line may have gotten air in it. This isn't a problem over time, but critical on the first fire up of a new top end.

My advice:
1. smooth out (or don't smooth out, your choice) your ports. My kit had chamfered ports, I just smoothed out the exhaust port.
2. Spray everything with carb cleaner, especially cylinder and piston. This will get rid of the sticky shipping oil in the cylinder.
3. Bathe the parts in a two stroke oil bath.
4. premix at 40:1. Maybe run 50:1 after break in?
5. Make sure there is plenty of smoke (especially in the first 5 minutes of run time).
It's a lot easier and cheaper to replace a fouled spark plug than it is to replace a top end that burnt up due to lack of oil.

Like I said, I was paranoid and proceeded with caution.

[drawkward]

Thanks for that. I'm going to go check out the postmortem of his cylinder kit right now.

As for the premix idea - very good advice. I do want to keep running the oil injector, so I'm going to just disconnect it for the first few tanks and premix, to be safe. I'm also going to make sure the fuel line has been bled and and free of the pure gasoline, and has the premix all the way to the carb. I'm also going to be cleaning my carb while I rejet it, so no pure gasoline will be left in there what so ever.

As for the carb cleaner on the cylinder - will do. I also heard (dunno if it was here, or elsewhere) that you should spray the cylinder walls generously with wd-40. Yay or nay?

Thanks for the advice. It is indeed much easier to replace a fouled plug then a whole cylinder.

[90GTVert]

If I chamfer, port, or otherwise mod an iron cylinder that will be stored for an extended period of time I spray it with WD-40 or coat it lightly with oil and put it in a zip-loc bag just to keep any traces of rust away.

[drawkward]

Mar 11, 2010 19:00:50 GMT -5 90GTVert said:

If I chamfer, port, or otherwise mod an iron cylinder that will be stored for an extended period of time I spray it with WD-40 or coat it lightly with oil and put it in a zip-loc bag just to keep any traces of rust away.

Must have been where I read it - The tech section. Always good info there .