Jetting Mikuni's?

[big jim]

I have 105 main jet's now and the needle clips are on the second grove from the top, needle almost all the way down, position. I aslo have 40 pilots. the fuel screws are 2 turns out. the bike had a stumble in the midrange and was getting 25 mpg. I ordered new needle jets because mine were wasted. I was thinking that when I orginaly test rode the bike no biggie. then I started reading about the coils and how they have the same symtoms as the needle jets bieng bad, crappy mid range. so I bought a set of tt 600 coils but when I took my bike apart I found PVK's so I think I'll leave them. So now that you are good and bored on to my question. This bike will be ran at sea level in ridiculious heat for the next 6 months and the next 6 with less heat. I have a set of 110 mains should I put them in? Where do you suggest I start with the needle and fuel screw? Should I go up on the pilot? Sorry I took so long Any help in this will be appriciated.

Brian

[nightrunner]

First I suggest you scroll down to my thread on rejetting the steamer.  It discusses the 98 with Keihins but the principal is the same.  In that thread someone also stated that the stock jets on his 95 were 105 and 40, so sounds like your's are stock.  First make sure your air filter is clean.  You can buy them as a unit or you can take it apart and clean the foam element.  If you want to rejet, I would suggest one size up on the mains (for stock exhaust).  That would be 107.5 but 110 should be OK too.  If you plan to run in hot weather, then erring on the rich side is better.   I would go up one size on the pilots.  This will be most noticable on easier starting and low end roll on accel.  Start with the screws at 1-1.5 turns out.   Without some means to measure CO concentration its hard to set the screws just right aside from reading the plug color every now and then and adjusting in 1/8 turn increments.  I would also raise the needles by one notch.  This will add response to 1/4 to 3/4 throttle range.   I have mine set up so it runs fine at low altitude and I can take the cap off the right side air intake if it starts acting up at higher elevations.

I am concerned about you getting 25 mpg.  You should get high 30's in stock trim.    That's low enough I would suspect some other problem.  Look for vacuum leaks, [and....what else guys?]  Are any plugs black?  Maybe excess fuel getting in somewhere.  Fuel leaks?   Holes in slide diaphragm.  

Also, have a look at this link.  Its good theory on M/C carbs.
http://hondanighthawks.net/carb14.htm (http://hondanighthawks.net/carb14.htm)

Lastly, with the Mikuni's you have a choice.  Both Dynojet and Factory Pro make a kit for the Tiger.

Good Luck

[big jim]

Thanks I'll try that. Factory pro is where I got my needle jets. I am pretty sure that is where my poor milage was coming from. they were pretty egg shaped and was way rich through the mid range. i'll go try to get some pilot's before I put it back together. What is the next size Up from 40? 41? I got some 48's I took out of a guys bike that would foul plugs about once a week, fzr 600 went to 42's. also I did a factory pro jet kit on that bike and they were very helpfull. this time I can't afford the kit so they weren't much help on the jetting. I already read your thread on jetting the keihins but was looking for more spesfic stuff uon the mis's which you confirmed what i was thinking. thank's
Brian

[big jim]

Also what about float level's?
Ok I just got back from the bike shop and it looks like the next pilot is 42.5 but they only had two. als all the pilot jets they had have holes in the sides like others I have seen but mine just have one hole in the bottom?

[nightrunner]

Holes in the side sounds more like a needle jet, but there are lots of different types of jets out there.  Each mfr has their own and then more than one type of carb in each series.   Sounds likr the ones you saw were for a different series of carb.  Many bike shops have boxes of jets to choose from and should be able to match the right series.  If not, I'm sure you can find a carb parts vendor on the interweb somewhere.    Should be able to get the stock needle jets too.  Anyway, one step up (2 #'s on a Keihin, and perhaps 2.5 #'s on a Mik) is a big step for a pilot and should solve any cold starting or low-end lag problems you have.   Part of the problem is that Triumph sized the carbs/jets such that the mixture screws are nearly all the way out from the factory.  There is very little room to adjust richer with the screws, so the next jet size is the only choice.  And it should put you in the low to middle of the adjustment range so you have room to experiment.

I would stick with stock needles.  On the Keihins we have to shim them.  Miks are easier with the notches.  I can't speak for the Factory Pro but the Dynojet kits do not change the pilots from stock.  On a street-riden bike, IMHO, the pilots are the most important.

Float levels, again IMHO, are a super fine tuning adjustment best left to the racing crowd.   I would make sure the floats are all at stock level.  When you get the other bits sorted out, you can tweek the float level if you want.

[big jim]

Thanks Nightrunner. I got the parts from Mudhen and the seal I need today so in the morning I'll start working on it. I found and ordered the right type pilots today. the next size is 42.5 They'll be here by noon tomorow. So I'll start with 110 mains 42.5 pilots needles in the middle and fuel screws 1.5 turns out. I should be reporting how it runs tommorrow afternoon if all goes as planed.

[big jim]

Got it running. It is lean through the mid range because I didn't get the pilot's The bike is on it's way to Bahrain now.

[nightrunner]

Good news.  You can install the pilots when you get there.  Post us a ride report from Bahrain!

[big jim]

Will do thanks for the help

[big jim]

Will do thanks for the help