I am getting my cylinders and new pistons today from the machine shop, just bored .060 over, and I am trying to decide if I should put everything back together stock to break it in?

The head was also milled .060", and I just picked up a set of Toomey T3s and a Pro-Design filter. Should I put it all back together stock to break it in, or am I going to have to rejet with the change in bore anyway? If that is the case, I am thinking that it would be just as easy to put the new exhaust and air cleaner on, and jet the bike with the new setup. Any suggestions? The old setup was stock air cleaner, stock exhaust, and .030" over pistons.

Also, from looking in the archives, it appears that for dune running at close to sea level, most guys are running 270 to 300 mains with my mods and no air cleaner lid, 30 pilots, stock needle location, and 1.5 turns on the mixture screw, does this sound like a good starting point?

Thanks in advance for any advice/help,
Dean

 

For starters, I would just put it all back together the way you plan on riding it. To break it in just go easy on it for a while and mix a little extra oil.

Now, about the .060" mill. You might want to take a look at your compression and keep an eye out for detonation. I believe that may be a little too much for pump gas.

I would jet it with the 300 mains and take it from there. If it is a little rich that's just fine for breakin and you can fine tune later.

 

I mentioned the detonation issue to the guy at the shop that is doind my machine work, and he assured me that this was THE hot setup that they have been doing for alot of the guys in my area. He said that you definately have to run premium, and CAN run AV gas but not required. I actually asked him about just doing .030" on the head because I thought maybe .060" was a bit extreme, but he said that they actually mill the head and reshape the domes for better combustion, and it works very well (really improves the bottom end I guess).

He actually recommended it above running one of the cool heads with interchangeable domes. I am sure that there are others that would disagree with that, but I have seen some of the Banshees that they have worked on, and they run well.

On the jetting, should I stick with stock pilots, or move up to the 30s? What about the needles?

Thanks for the help,
Dean

 

Is your crank welded? I hope so you have crossed the safe line and if it isn't get in done right now or you'll be sorry! If you spin the crank it will destory your motor.

 

Isn't it really only unsafe if I allow the engine to ping? As long as I run fuel that eliminates the detonation, I think I should be ok. I guess I am also puzzled as to why this shop would make a recommendation to do this if there are known issues with the cranks in Banshees with high compression.

I'll call and see if they have already done the work.... this is something they recommended, I just told them to clean it all up for use with the new pistons.

Anyone else have any input?

Dean

 

I just spoke with the shop to make sure I wasn't getting in over my head (no pun intended, sorry couldn't pass that one up[img]i/expressions/face-icon-small-happy.gif[/img]). Anyway, he mentioned that they totally reshape the domes, which brings the compression back down to a reasonable level (still more than stock, but not insane).

Dean

 

Well, a VERY ROUGH guideline is to keep your compression below 150PSI or so to be able to stick with premium gas. The thing about the crank is that is is a press fit unit and will come loose and spin if you have too much compression and/or power. Unfortunately, that is the main weak are on the Banshee you have to deal with when you start getting into more mods.

I would recommend that you buy a compression gauge and keep an eye on that. Also, pull your plugs every so often and make sure they are properly colored and not showing signs of detonation. I'm sure your machine will be fine but it never hurts to keep an eye on what the shop is doing and question them if you're not comfortable.