Tri-z 250 Engine Question about excesive smoke and compression.

[MN250R]

The Tri-z i picked up from my friend starts right up. But man does it smoke haha. ALOT Im running 32:1 lucas 2 cycle oil. There is also alot of oil coming out the back of the stock exhaust pipe.
I had it running in my yard and it was running strong for like 5 mins then started loading up and smoking alot. I checked the compression also and it was 165 without throttle open and 170 with throttle open. Is that good ?
I went through the carb. Funny thing though is when its idling, i can screw the air screw in all the way with my finger or all the way out and the motor doesnt change rpm at all :wondering. Maybe float is off or something.

ANy help would be great.

http://img718.imageshack.us/img718/1549/dsc00593zm.jpg (http://imageshack.us/photo/my-images/718/dsc00593zm.jpg/)

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[tecat-z]

Your compression readings are right in line with a healthy stockish Tri-z engine. Try and lower you needle 1 clip, and go down 1 main size. If it helps to clear things up, fine tune it from there.

[Cave Rider]

I am not sure just how bad it is smoking but check your crankcase breather as well, I have seen them get clogged with mud... it causes excess crankcase pressure, ultimately causing oil to force past the westside seal. in other words be sure you're not consuming transmission oil. hopefully the cases arent cracked from a previous engine failure either. good luck with her..

[MOTOMAX27]

check your plug. check the mix again to be on the safe side. if everything is good, like tecat-z said mess with the jetting.

[jmax857]

I wouldn't drop a jet size blindly without doing a plug chop, is the smoke black? Does it smell sooty? Or like burning premix?
If you have the tools, do a leakdown and see if its leaking through the oil seal at the crank on the clutch side.
If you know how to do a proper plug check, do one and post a pic and it can almost be pinpointed by that alone.

[MN250R]

it smells like burning premix. the smoke is blueish white. i will check the jetting again also. how do you do a leakdown test? when i did a compression test it held at 170 for a fee mins until i releases the air on the guage . thx for all the replies!

[jmax857]

White usually means bad head gasket and you could be burning antifreeze. If you are your plug will come out with a white buildup on your plug when the plug chops done at w.o.t. Check your fluid level, does it smell sweet?

[El Camexican]

Is it needing to run on the choke for a while, or will it start without it in cold weather? If it starts without the choke, or only needs the choke for a few seconds in the cold and all the jets are stock (i.e you don't have a monster pilot jet in it) and that air screw is not doing anything when turned you may have plugged up an air orifice while in there, or as you said the float may be set too high or leaking. I'd look there first. If you get the screw working and it still smokes after some good driving I'd start looking at the seals as some of the guys mentioned. BTW that thing looks great, and so does your shop floor!!!

[MN250R]

Did a leakdown test on the engine with this homemade tester. It held 6 pounds for over 20 mins no problem. After looking at the jets, the pilot was 55 and should be 45. plus i had no idea what the main was. couldnt read it. im putting all the jetting back to stock. ps i was turning the idle screw not the air screw lol. will report back on my findings. thx for all the replies

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[jmax857]

Stock jetting for an 85 should be 470 main, 45 pilot, needle in the 2nd clip, and air screw 1.0 turn out. Do you have any waftermarket parts on your z?

[gus]

That's one nice clean z you got there by far the cleanest z I've seen. I would also check the carb setting

[MN250R]

Well i cleaned the carb with seafoam, let it sit over night, blew out all the air passages the next day. then i installed all new jets....45 pilot...470 main and yamalube 24:1 92 octane. Bike starts right up. Still smokes the same out as it did at 32:1. I let it warm up and tried to make some adjustments to the air screw. Turning the screw all the way out did not raise the rpms at all. I wonder if the pilot jet is to rich. Maybe i should go down one more step. One other thing thtas kinda wierd. I cant get the bike to idle with the idle screw screwed all the way in. Its like it doesnt raise the slide enough. I have to adjust the cable up by the handlebars to get it into an acceptable idle range. But once i do that, if i turn the handle bars to the right, the throttle revs a bit. I will have to look into it some more i guess. Thanks again

Ill get a video up in the next day or so.

[gus]

you said the throttle revs a bit when you turn to the right? i had that same thing happen to me with my are it turns out that the throttle cable was going under the radiotors and was a bit short so everytime i would turn the handle bars it would rev up.... did you check for air leaks?? have you done a plug chop yet? that well also help on how rich/lean your running

[jmax857]

The throttle to the right is from tightening the cable at the top of the carb. Which is definately not the proper way to set your idle. You need cable slack to operate properly. Pull the slide and see if it is the proper one for the carb. You might have a 86 slide in there. I highly recommend not using the bike with the cable like that. Also check your needle and see what is in there.

[MN250R]

ya im not riding it until the cables fixed thats for sure ill look at the slide tonight and report back

[jmax857]

Needle should be in position 2, and the slide should be a number 2.
Also check your reeds.

Edit:
Also you can almost rule out an air leak, normally an air leak causes a "high idle" or an ustable idle. And you did a leakdown and it held.

[MN250R]

Well i know i had th eclip in position 3. I will move it to 2, and check the needle number and slide number. I will also take a look at the reeds

[MN250R]

Well after looking at the parts in the carb, the slide says 2.0 which is factory. But i did notice the needle was nice and bent. When i roll it on the table it wobbles. That cant be good. It looks to be a 6h3-3.
I have one off another mikuni carb but its a 6f3. Ill have to try and find a 6h3 needle.

[MN250R]

Here is a video of it running. Got the needle straightened out. Ill have to do a plug chop on her yet. Still kinda smokey haha


http://youtu.be/hQN1OruUqNY