breaking in new crank

[fatboyslim]

Just put my new crank in with newly plated cylinder and top end. Just wondering about the best choice for heat cycles, pre mix ratio and throttle application for the breaking in process. 05 yz 125. Thanks. Happy New Year!

 

[125rmcrazy]

20:1 mix. use the entire rpm range without keeping it pinned or lugging the engine. 1 full tank of fuel like this and then switch up to 32:1 or 40:1

 

[fatboyslim]

20:1 seems way to rich and i though you were supposed to just keep the engine warm

 

[rpm12505]

20:1 :yikes: Where do you guys get this stuff?
Sounds too lean a fuel mix to me.

 

[whenfoxforks-ruled]

There should be enough oil during assembly. You do not need to screw with the oil ratio's. Heat cycle a couple of times, easy on the throttle a couple of times.

 

[fatboyslim]

I just did my first heat cycle and now the bike is cooling but there is a loud pinging sound sounds like its in my exhaust. When I put my hand on the exhaust it gets quieter but its still there. I do have a beat up sst pipe and it did pi a little before I put the new crank in. Is this normal?

P.S. sounds like someone is makin popcorn in the pipe.

 

[125rmcrazy]

guys i've got the factory manual for my bike and it states 20:1 oil mix at ALL times. no doubt its a bit rich for normal riding. but for break in i wouldnt put a drop less. but it is whats written in the factory suzuki manual.

 

[fatboyslim]

Could the ticking be the powervalve or something?

 

[whenfoxforks-ruled]

Crazy, different manufactures spec their engines to run at a particular ratio, and that is that! KTM has some of the wildest, 50:1. The boy's from amsoil like 100:1. 05 yz 125 at 32:1, 91 rm 125 at 20:1, believable. Fatboy, it should just be metal contracting. How does the plug look?

 

[rpm12505]

guys i've got the factory manual for my bike and it states 20:1 oil mix at ALL times. no doubt its a bit rich for normal riding. but for break in i wouldnt put a drop less. but it is whats written in the factory suzuki manual.

I think oil technology has changed alittle in the past 17 years, but I could be wrong. My 05 manual says 32:1

 

[fatboyslim]

spark plug looks normal, little bit wet but the bike starts fine and has good throttle response. Could it be the power valve somehow?

 

[whenfoxforks-ruled]

The power valve does not move by itself. The noise I believe is the expansion chamber, expanding and contracting.

 

[fatboyslim]

So is it wrecking my exhaust or anything or is it just b/c its cold herecuz the bike never did it before well not as loud.

 

[whenfoxforks-ruled]

You are suffering like a parent over their sick kid. The stretching is normal.

 

[rennat_2006]

are you sure the bike isnt pinging?

 

[fatboyslim]

I'm kinda sketchy about this cuz i just spent a bunch of money on a bike i haven't hardly riden and i need to ride it this summer cuz I missed out last year. Yes it is like a pinging sound in my exhaust at idle, like there is something bouncing around in there.

 

[rpm12505]

Cracked pipe?

 

[BLACKeR]

stretched and loose pipe spring rattling? go through and touch all the pipe springs if it stops rattling when you pinch a spring thats what it is.

 

[whenfoxforks-ruled]

I was under the mis-information it was doing this after it was turned off. You need a listening device, like a half inch wood dowel rod, or a stethoscope and isolate the noise. Was there any mods done to the engine?

 

[rennat_2006]

What are you running in it for fuel(octane)?

 

[fatboyslim]

91 octane mixed at 32:1, things done to engine were new crank, piston kit, nikasiled cylinder. Pipe is not cracked but does have lots of dents at curve of the expansion chamber though, could that be the problem? My local shop here said it could be from the higher compressed air going over those bumps in the pipe. Maybe?

 

[fatboyslim]

Any one have any answers?

 

[rennat_2006]

What kind of compression do you have?

I dont know how it works with your bike but i know on my KTM's you have to set the "X Dimension" which is the distance between the head and the piston. This is what sets your compression ratio in the engine, It is adjusted with different thickness or stacking of cylinder base gaskets. If your compression is too high it could cause pinging/preignition which is what you may be hearing. I know of a guy with a ktm500 that had this problem and he had to step up to a vp race fuel.

Pull the head off of your bike and take a look at the piston to see if your bike is pinging. Take a look at these websites for what im talking about...
http://www.dansmc.com/gas.htm
http://www.ultralightnews.com/enginetroublshooting/pistonfail/pistonfail2.htm This is off of a Nitro R/C airplane but same conditions apply because they are both 2 strokes.

 

[whenfoxforks-ruled]

Under optimal conditions the pulse and sound wave exit the exhaust at the same time. If something is changing this then yes you can have issues. I do not believe it will hurt the engine, performance yes.

 

[fatboyslim]

I think it may be more compressed air passing over those big dent in the bottom of my expansion chamber b/c it was a little tingy before I rebuilt the engine so I hope it's going to be OK.