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View Full Version : how will my tri z perform with 38 mm flat side on it


TRI-Zbrian
10-26-2003, 06:09 PM
hey guys i just bought a freshly rebuilt 85 tri z 250 with a 6 speed lower half. the engine is resleaved all back to std bore and hasnt even had a tank of gas threw it yet and is bone stalk. my problem is the last owner threw a 38mm flat side carb on it and never jetted the carb so it runs like trailprotrailprotrailprotrailprotrailpro but does run. about how much will it cost me to get the carb jetted to the yamaha rench report specs.

also in a a month or two after i get the carb taken care of im going to get a dg pipe and silencer and a set of boysen power reeds. will it be a night and day difference from switching from the stalk 32mm carb to a 38mm flat side carb what should i expect/
200xer
10-26-2003, 07:00 PM
I'd expect I little less low end and a ton more mid to top end.
200xman
10-26-2003, 07:25 PM
Just remember that you will have to rejet again once you get the pipe and reeds.
Tri-Z Pilot
10-27-2003, 03:12 AM
Visit www.thunderproducts.com/dial_a_jet_techpaper.htm This has to be the number one upgrade for anything that has an engine, jetting changes controlled by a dial.
J.D.
10-27-2003, 01:02 PM
If your engine is stock I think a 38mm flatside would probable choke it. If anything move up to a 34....not a 38. Wrench Report has nothing to do with jetting your carburetor. Wrench report is dealing with engine mods. The jetting specs they give you are just a base point and which you will still have to refine to your local area, due to altitude and weather. Have fun!
TRI-Zbrian
10-27-2003, 06:10 PM
im shaving the head, putting a dg pipe and silencer, and boysen power reeds, and a k&n air firlter. so i dont think it will be real choked
TRI-Zbrian
10-27-2003, 06:34 PM
i just read that dial a jet thing and i am defanetly getting that if it works the way it ses it does it should do wonders on a 2 stroke say by by to fould plugs and stuff like that.
Dynofox
10-27-2003, 08:19 PM
If you have your bike jetted right it should never foul plugs. My tri z never fouled a plug and I can't even remember the last time I had to change a plug in a sled and I've been riding them for over 12 years. Check with others who might have the same carb on their 250's so you could atleast get a possible base line for jetting. You have any idea what the carb came off?
TRI-Zbrian
10-28-2003, 12:42 AM
the guy sed he got it off of a yz 125 and he put the stalk size main jet that came on the tri z with the ariganal carb in it so it has a 470 main i believe. and it runs like major crap but runs alright but runs beter when u leave the choke on so i want to get the right jets for it i just need to know what to get would i be alright doing the wrench report jetting on it and going from there
samster143
10-30-2003, 07:08 PM
If your machine runs better with the choke on.....I believe you are running dangerously lean and may hole yer piston. Maybe I am wrong, but you need to do something soon.
Dynofox
10-30-2003, 08:00 PM
I agree with samster143 on this one, if it runs better with your choke on your motor is running lean. Have you looked at your plug yet?
Kilborg
10-30-2003, 08:10 PM
With a larger carb and nothing else, your going to gain topend and midrange at the expense of lowend. This is okay, as Z's have a good lowend pull and the new carb won't drastically effect the powerband to the point where its a whole new engine. Expect a smoother, more manageable topend with a little bit of a harder hit. With other mods, you can easily gain back the lowend you lost.
TRI-Zbrian
10-30-2003, 09:17 PM
its hasnt been driven yet untill the carb is dialed in the plugs actauly reed like it is running realy realy rich i think the prob theer is the wrench report sed that i should run a 350 main jet but the last owner did not no this and he put the stock size main jet for a try z in the car wich is a 470 and i think that is the reason it is running realy realy rich
i havent ridden the bike at all just took it for a quick spin up the road i believed him the engine was all new cause he showed me a bunch of dated receets (spelling?) and the bike had a cover over it and was covered in dust like it was never riddin and he told me it hasnt even had a tank of gas threw it yet.
J.D.
10-31-2003, 12:15 AM
Plop in a 350, work from there. Guys, with the choke on, that makes it leaner, that's why it runs better. He's running insanlely rich with stock jet in a bigger carb, when he puts the choke on it makes it run leaner, making it run better.
TRI-Zbrian
10-31-2003, 02:56 AM
ill give that a try thanx for helping me out
200xer
10-31-2003, 01:36 PM
choke on = more fuel or less air.

Make sure you are actually putting the choke on and not off (or visa versa). Since it is a flatside it probably has a choke fuel circuit and not another butterfly. If the carb has just a knob it's up to choke. If it is a lever it is probably down to choke. the lever just needs to raise a barrel in the carb to turn on the choke on.
HypnotizeMindz
11-01-2003, 09:43 PM
how much do those dial-a-jet's run for ?
J.D.
11-02-2003, 01:39 AM
choke on = more fuel or less air.

Make sure you are actually putting the choke on and not off (or visa versa). Since it is a flatside it probably has a choke fuel circuit and not another butterfly. If the carb has just a knob it's up to choke. If it is a lever it is probably down to choke. the lever just needs to raise a barrel in the carb to turn on the choke on.

None the less there homeboy, it will still run leaner with the choke on. That's why it runs better with choke on. Depends on what dial-a-jet you need Hynotize, one for a Tri-Z costs 69.95.
atc86r
11-02-2003, 12:31 PM
I didn't see if it was kehihn or mikuni.
Curtis-Tecate3
11-03-2003, 10:27 AM
People, If your bike runs better with the choke on then the first thing to do is to make sure your jets arent clogged up. 90% of the time that is what you will find unless you a doing a carb swap from a different bike.

Curtis.
TimSr
11-03-2003, 01:33 PM
People, If your bike runs better with the choke on then the first thing to do is to make sure your jets arent clogged up. 90% of the time that is what you will find unless you a doing a carb swap from a different bike.

Curtis.

I agree completely, and along with making sure jets are clear, take them out, and make sure the orifices are completely clear.

I choked bike runs much richer. If you dont understand what the choke circuit accomplishes on the newer carbs, look at one of the older Honda carbs that the choke lever closes a door in teh carbs intake, cutting off most airflow.