Jetting.... where to start?

[MIABanshee]

Im rebuilding my shee and would like some recomendations on where to start jetting. It is going to have a pro design air filter, modified lid with vents, bored carbs to 28mm, boyesen reeds, stock cages, wiseco pistons 20 over, modified head for pump gas, trail porting, toomey t5's, advanced timing +4 and I think thats it. Im gonna be running castor 927 at 32:1

 

Located in Miami FL at sea level, temperature usally around 60-90 degrees.

 

Want to know where to start on pilot, mains, and needle clip and it has toomey needles.

 

Also what jetting should i use to break it in?

 

Thanks guys

[bigboybanshee]

I would aim for 300, maybe 310 on the mains depending the extent of the porting, and a 27.5 pilot jet. My T5's like the needle clip on the second clip from the blunt end. That would be my starting point.

[MIABanshee]

I would aim for 300, maybe 310 on the mains depending the extent of the porting, and a 27.5 pilot jet. My T5's like the needle clip on the second clip from the blunt end. That would be my starting point.

306331[/snapback]

 

What should I run for break in, just to be on the safe side?

[bigboybanshee]

Where were you at on jetting before the rebuild? What mods were you running before?

[kw04]

for break in you could probably adjust the air/fuel screws so its a little rich.

[MIABanshee]

for break in you could probably adjust the air/fuel screws so its a little rich.

306631[/snapback]

 

 

Before I had only Toomey T5's and a 2-1 air filter.... I was running 290's but Im switching to an airbox now.

[bigboybanshee]

Well, you won't need to rejet for the milled head, and not for the .20 over pistons either. Same goes for the advanced timing mod. Being that you are adding the airbox and removing the 2 into 1 filter, you would want to go leaner on the main jets. BUT, since you added porting, that may require you to go richer on the jetting. When I bought my reeds it said in the package that it would make my engine run richer but I never really noticed that at all. Your pilot jet shouldn't be affected at all by these mods....Honestly, just run the jets you ran before the work, especially since the most critical part of breaking it in is the heat cycling, which your main jet doesn't even have a role in....Even if it is slightly lean with the 290 main jets, it's not gonna be too lean to where it'll smoke your rings or anything.

[MIABanshee]

Well, you won't need to rejet for the milled head, and not for the .20 over pistons either. Same goes for the advanced timing mod.  Being that you are adding the airbox and removing the 2 into 1 filter, you would want to go leaner on the main jets. BUT, since you added porting, that may require you to go richer on the jetting. When I bought my reeds it said in the package that it would make my engine run richer but I never really noticed that at all. Your pilot jet shouldn't be affected at all by these mods....Honestly, just run the jets you ran before the work, especially since the most critical part of breaking it in is the heat cycling, which your main jet doesn't even have a role in....Even if it is slightly lean with the 290 main jets, it's not gonna be too lean to where it'll smoke your rings or anything.

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OK thanks, I'll throw in some 300's just to be safe and see how it runs if anything I'll go down to 290.

[canyncarvr]

If you haven't taken a gander at this...check it out:

 

http://www.dfn.com/benkaren/jetfaq.html

 

Note he does recommend a jetting change for timing adjustment. Most would. Gives you an idea that not everyone's point of view is the same.

 

As you stated, it's always best to start rich, go lean.

[richybanshee]

Advacing the timming and more compression makes the shee run hotter. Also what actually cools the piston is not exactly the water around the jugs, is the fuel. I do not know if you have notice but when a shee runs lean it overheats and coolant starts liking and creates ugly spots in the pipes. You can smell it also. The cure is go bigger on the mains before you melt the crown of the piston. Happened to me a few years ago, so I learned jetting the hard way. JEJE!!!

 

Really, I did a lot of reading and troubleshooting before understanding jetting issues.

 

To be safe, I say go to a 340 main and start down sizing if needed. After your are done with the mains check the jet needle. Finally the pilots, maybe up to 30's.

 

Just START EXPERIMENTING this is how you will learn.

 

Many of us can give you an idea, but you are the lead scientist. GOOD LUCK

Edited January 19, 2005 by richybanshee

[Banchetta]

Advacing the timming and  more compression makes the shee run hotter.  Also what actually cools the piston is not exactly the water around the jugs, is the fuel. I do not know if you have notice but when a shee runs lean it overheats and coolant starts liking and creates ugly spots in the pipes. You can smell it also. The cure is go bigger on the mains before you melt the crown of the piston. Happened to me a few years ago, so I learn jetting the hard way. JEJE!!! 

 

Really, I did a lot of reading and troubleshooting before understanding jetting issues.

 

To be safe, I say go to a 340 main and start down sizing if needed. After your are done with the mains check the jet needle. Finally the pilots, maybe up to 30's.

 

Just START EXPERIMENTING this is how you will learn.

 

Many of us can give you an idea, but you are the lead scientist. GOOD LUCK 

308483[/snapback]

Nicely stated. I'd also start w/ 330-340 range. The larger bore in the carbs will increase the jet size a little as well as the porting..Better to start rich and work down..I'd start w/ 330 mains, 25 pilots and needle in the middle clip to start and go from there.

[MIABanshee]

Nicely stated. I'd also start w/ 330-340 range. The larger bore in the carbs will increase the jet size a little as well as the porting..Better to start rich and work down..I'd start w/ 330 mains, 25 pilots and needle in the middle clip to start and go from there.

308710[/snapback]

Thanks alot guys, I found a set of 340's so Ill throw those in and see how it runs.

[richybanshee]

Keep us up to date with the tests.