Is it possible to improve top speed without changing tire size or gearing? Here’s my dilemma, I have an 85 Yamaha Tri-Z 250 (2 stroke trike) which a few months ago only had a UNI air filter with the stock carb jetted (Mikuni VM 32mm) airbox lid on, Boyesen Pro Reeds and the stock pipe with an Answer silencer (similar to DG). When I raced my brothers Banshee (with FMF pipes, silencer, KN Filter and jetted carb) we were dead even from stop to top speed (roll start in pavement). Recently I installed an LRD pipe and silencer, a Mikuni TMX 36mm carb and rejetted it myself for no lid use. When I raced my brothers Banshee again with all my new mods I was as fast at low end but slower at top speed (Full Throttle). My brother has only added a cool head since then and I also raced a friend’s banshee and he was faster top speed so I do not think the cool head makes the difference. Is that possible or am I paranoid? How can I be slower after getting an aftermarket pipe & SILENCER AND a bigger carb without airbox lid? Am I missing something? What can I do to get more top speed?

 

Sounds like you didn't do a good job jetting. [img]i/expressions/face-icon-small-shocked.gif[/img]

 

When I first jetted my main it was very rich (I was running a 470) and it would not run at all at full throttle the engine breaks up when at full throttle. Then I switched to a 440 and it ran fine at full throttle for about 4 seconds then make a small break but keep running strong, this was with the lid on. Then I remove the lid with the same 440 main and it ran great but I went down to a 420 main afret that to make sure it will run without blubbers"" with and without lid. Am I wrong? Should I go to 440 main again? Will that make a difference? I thought 2 sizes main will not make any difference!

 

I don't know sht about crazy 440 jets I run Kehin so it's got different #'s

 

You changed the jet to make it richer, but then removed the airbox which effectively made it LEANER.

Do a plug check WITHOUT the lid on if that is how you intend to ride the trike.
You MAY have leaned it out too much by removing the lid.

When making changes, only do one thing at a time. Otherwise, you are jumping all over the place, and won't know where the heck you are at.

 

The real question is would it make a difference if I am running a little bit lean? I went down only 2 sizes on the main. Would the ideal main jet makes me have more top end RPMs to affect top speed?

 

The main jet will Definately affect top speed amd RPM. That is the carburator cicuit that it controls. If too lean, you run the risk of not only a lack of power/rpm's, but also the risk of overheating, and subsequently seizing the motor!

Do a plug test at full throttle!

 

Got enough quads there, 2Fun???? haha! I get knocked by my friends for having 2 and wanting a 3rd!

 

<< Got enough quads there, 2Fun???? haha! I get knocked by my friends for having 2 and wanting a 3rd! >>



2stroke4ever;
You can NEVER have enough quads!! LOL!![img]i/expressions/face-icon-small-happy.gif[/img]

Actually, I will probably be selling the two Banshees, and the Blaster when I get a chance.

I used to have two more Banshees, an 87', and a 99', for a total of seven quads, but they (87 &amp; 99) got ripped off last summer! GGRRRrrrrrrrrrr..........!!!!!!

When I get out of college (for the 2nd time!), I will probably collect a few more! Probably mainly 250R's, but I may sneak in a couple of 4-strokes, who knows.........[img]i/expressions/face-icon-small-wink.gif[/img]