85 tri z- blue/white smoke, black wet plug

[TRI-CYCLE]

Ever since I got my 85 tri z, it will only run with its mikuni choke lever in the up position. Runs well too. As soon as I push the choke lever down, it bogs out to death.

It has a dg pipe and what looks like a k&n filter. Id always assumed it needed a slightly bigger jet due to the mods... so last night I rejetted it, I put the 500mh jet in, thinking id rather be rich then lean.

As always it blows bluish white smoke, runs great on choke, the needle clip is adjusted on richest side, and the plug comes out wet, I can also hear a weird pinging from jug that sounds as if it were running lean... motor has been rebuilt FYI.

Also I'm getting a lot of oily black fluid out of the exhaust, but still bogs out to death with choke lever down... im frustrated and overly confused.

Its gotta be getting plenty of fuel if its coming out of the exhaust.... so why the hell with the choke up (on-for more fuel, less air) would it run better... I've been in the carb multiple times to find it spotless everytime

Mixture screw I have out about 1.5 turns, and idle screw the same... I've messed with them briefly but to me seems like wasted time to adjust them while engine running on choke only

[TRI-CYCLE]

I also forgot to mention, the bike is very hard to start cold. But a quick spray of ether brings it to life everytime

[El Camexican]

I've been in the carb multiple times to find it spotless everytime

"In the carb" as in took the bowl off and it looks clean, or in as in took out every jet and made sure all the holes are clean?

Is your pilot jet clean? No tips broken off of any needles? Have you checked your float height? Is your fuel return line properly plumbed?

It sounds like you have at least a couple problems with your fuel system as it seems you are lean at the bottom and rich everywhere else. I would not worry about that engine noise yet if at all. A knock could be a loose rod, but pinging is either a slightly loose piston, or nothing at all. Can I guess that you are new to 2 strokes?

[barnett468]

Hello


Here are a couple of suggestions others will have helpful ideas also.

Xxxxx

Ever since I got my 85 tri z, it will only run with its mikuni choke lever in the up position. Runs well too. As soon as I push the choke lever down, it bogs out to death.

Does it idle?

Sounds very lean, could be jetting or low float level or plugged pilot jet.

Check float level.

Remove float bowl and spray carb cleaner using thin plastic nozzle into pilot jet and make sure it comes out bore in carburetor bore.

xxxxx

It has a dg pipe and what looks like a k&n filter. Id always assumed it needed a slightly bigger jet due to the mods...

Yes slightly richer than stock but what is stock?

xxxxx

last night I rejetted it, I put the 500mh jet in, thinking id rather be rich then lean.

What is a 500mh jet?

What jet did you tremove?

What sixe is your pilot jet?

xxxxx

As always it blows bluish white smoke,

Could be rich or rich oil mix or bad crank seal sucking oil from crankcase.

What oil and ratio are you using?

Might need to do a leak down test, one of us can try and determine that for you.

Xxxxx

runs great on choke, the needle clip is adjusted on richest side, and the plug comes out wet,

May just be from the choke being on at idle when you shut it off.

xxxxx


I can also hear a weird pinging from jug that sounds as if it were running lean... motor has been rebuilt FYI.

Not good, might have excessive compression, suggest immediate compression test with good gauge with short hose with small id. Don it with gas off fuel bowl dry and throttle wide open.

What octane gas are you using?

Needs at least 93.

Don’t ride until it is correct or serious damage to piston/cylinder may result.

xxxxx

Also I'm getting a lot of oily black fluid out of the exhaust,

Could be left over build up from previous worn cylinder, rings, piston etc. One of us will figure it out.

xxxxx

but still bogs out to death with choke lever down... im frustrated and overly confused.

Its gotta be getting plenty of fuel if its coming out of the exhaust.... so why the hell with the choke up (on-for more fuel, less air) would it run better... I've been in the carb multiple times to find it spotless everytime

Mixture screw I have out about 1.5 turns, and idle screw the same... I've messed with them briefly but to me seems like wasted time to adjust them while engine running on choke only

xxxxx

I also forgot to mention, the bike is very hard to start cold. But a quick spray of ether brings it to life everytime.

Does it star easier with or without choke?

[TRI-CYCLE]

New to 2 strokes yes. I've pulled the carb apart, sprayed carb cleaner through all holes... never pulled the mixture screw out while cleaning carb before... but I pulled mixture screw out yesterday expecting it to come to a point at the end of the screw (I'm guessing this is the pilot jet?) The end of it was flat.. not like somebody overtightened it... but flat on the end as if it was supposed to be that way or it was filed down. That seemed odd to me but maybe that's the way they were?

I also adjusted the floats some, the rejetting kit instructions said I could do so, so I took initiative (experimenting) by slightly bending the floats upwards allowing the bowl to fill a little more.

From what I can tell, all fuel lines and vacuum lines are where they need to be and working correctly. A few weeks ago I pulled all lines off engine, checked all fuel lines to make sure they were flowing, not plugged. Also made sure the fuel pump was pumping

[barnett468]

Hello


Your main may not be way too big, we'll see.

Install a clean new white plug for jetting test.

How old is current plug?


OEM Carb settings

Pilot 45
Main jet 470
Idle mix screw out 1 turn from full in.
Float height 31.3 millimeters or 1.23 inches see page 3-6 for instructions on how to set it.

OEM MANUAL CARB VIEW AND SETTINGS PG 3-2 and 3-6 CLICK ON BLUE LINE AND WAIT UP TO 20 MINUTES

http://www.oscarmayer.net/atc/manuals/Yamaha/tri-z_250_servicemanual.pdf

[barnett468]

Hello

Look at the pages in the manual it will show you what is what in the carb then reply back with info.

Mix screw is on outside of carb and typically very pointed.

[TRI-CYCLE]

Yes bike idles on choke, bike will really only function on choke. With ether it'll start on either setting normally, but without choke it'll slowly die again.

As far as jets go, I don't know how you guys determine sizes. But I ordered a jet kit from 6 sigma on eBay. company asked for what mods the bike had then sent me a jet kit specifically for the bike. Kit came with a 460mh jet, a 480mh jet, 490, and 500. Im guessing stock must be a 470.

When I say jet kit I mean I just replaced the small brass like 8mm jet that goes from bowl to carb needle and slide. That's it.

Octane was my next subject.. I live in the oil patch of nodak.. I been running 91 octane at about a 35:1 to 40:1 ratio and use husquavarna 2 stroke oil I can get at the hardware store.. I was beginning to think my octane wasn't high enough and really don't trust the crap oil so I bought some yamalube 2 stroker oil last time I was In the big city.

Maybe I should add some higher organs fuel, and reduce the jet size down to the 480 or 490 jet?

[TRI-CYCLE]

Ok I replied before seeing your other reply. I'll check it out

[Mosh]

It sounds to me as if either your are too either lean on your slow jet/pilot jet wheter it be the wrong one, or damaged.
OR you have a vacumm/air leak. that is why you need the choke on to make it idle. Normally you will get that air leak at the base of the jug on the Z, the intake area, or around the vacumm fitting for the fuel pump pulse line or line itself.

You want to carefully spray some brake cleaner (It is flameable so make sure the engine is not too hot) around those areas and see if the idle changes. If it changes dramatically then repair the air leak.
Also you want to make sure that the vacumn line to the jug is not full of raw fuel from a ruptured fuel pump diaphragm.

The 85 Z was jetted slightly rich from the factory. In my experience with a stock carb rarely do you have to run a larger main jet.
Make sure all jets are the correct ones per service manual, put your needle back to stock posistion, then test for air leaks.

[TRI-CYCLE]

Thanks mosh, like I mentioned above, the air fuel mixture screw is flat on the end if I unscrew it and pull it out, the end that should be at a point looks like its been filed or something. I hate to say that though because I'm not sure if it is factory or not.

I'll try the air leak trick, your saying there's an airline that goes from the jug to the fuel pump?

[TimSr]

Remove the idle air screw completely ("fuel mixture screw"). Take the bowl off and remove the pilot jet. Its the one that is recessed and looks like a strainer. Make sure holes in it are open, especially the center one, which is probably clogged. Then blow carb cleaner through the empty hole the jet was screwed into as well as the hole the air screw was screwed into. Remove the choke plunger and do the same. Blow through EVERY hole, and make sure it comes out somewhere else. Check the size of the pilot jet while you have it out, and make a note of it. It should be stock size, which I don't recall off the top of my head, because you'll never have to change it for minor bolt on "mods". After the choke issue is resolved, put your 470 main jet back in, set the needle clip to the middle, and from this starting point, drop main jet sizes until you hit the happy zone. You'll probably end up in the mid to low 400's.

[TRI-CYCLE]

Great news! I missed the pilot jet because its hidden so well. It was very plugged up. Switched to the 480 main jet. Fired first kick with an empty bowl of fuel without choke. Couldn't believe it. Exhaust is tan colored.

Although it is blowing quite a bit of smoke.. its now the right color. Very responsive.. just trying to get it to idle now, maybe I do need a smaller jet then a 480.. I'm thinking to rich right now. By the way, pilot jet is a 45

[El Camexican]

Your crankcase might be full of old fuel and oil and your pipe and silencer are likley full of goo. If it seems to be running good take it for some good high RPM rips and get it good and hot. Expect lots of smoke. You may want to change your muffler packing soon as well.

If it still seems to be loading up with fuel after that you may have another problem besides the main jet size. The stock main jet may be too big to run perfectly, but that shouldn't cause raw fuel to blow out the pipe.

Oh, and BTW I think the air screw in that carb came with a blunt tip, so don't worry about that.

[TRI-CYCLE]

Went and test road it with factory 470 jet, choke and it runs great. No choke and it bogs down some but at high rpms it seems to keep up good.. I'm thinking it is lean.. but I'm no expert. Not a whole lot of smoke. But on choke the idle is much higher. It barely idles if at all without choke. Messed with the mixture screw quite a bit, its at least 2+ turns out right now running best. Throttle settles to idle slower then it should it seemsand not a whole lot of smoke compared to bigger jets I experimented with earlier.

I've replaced the plug, and added octane booster to a full tank if fuel with no improvement. Could sparkplug gap cause any of the problems I'm having,

[El Camexican]

How cold is it there right now? Less than 40F? It sounds lean at the bottom, but if your pilot jet is lean then it should run better with your air screw nearer to closed, not 2 turns out. Try 1 turn out and see if it doesn’t run good without the choke. Have you checked your float height properly? Is your needle set in the center clip? And yes your plug gap is important.
BTW if it is bogging at the top it is likely rich. As said earlier they came a little rich and usually a lean main jet will let the engine scream where as a rich jet will hold back the revs. That is why it is always best to start with a rich main and keep going down one size at a time until it runs clean and leave it. If you start off too lean the only way to know is a plug reading and that can be a PITA. I prefer to get things running right by feel and sound and then checking to see what the plug looks like.

[barnett468]

Hello


The following are my opinions and suggestions only. Others may vary. It would be helpful to me and possibly others if you answer ALL the following questions. It might be easiest for us to read if you post your answers in line order fashion and NOT one long paragraph.

xxxxx

Great news! I missed the pilot jet because its hidden so well. It was very plugged up. Switched to the 480 main jet. Fired first kick with an empty bowl of fuel without choke.

Does it still start easily without choke when motor is COLD?

Do you EVER need the choke to start?

What is your approximate air temp outside when starting?

So far it sounds like you pilot jet size is ok if not slightly large or you FLOAT level is too high

Check float level, I previously posted the spec and manual instructions for you.

xxxxx

Couldn't believe it. Exhaust is tan colored. Although it is blowing quite a bit of smoke.. its now the right color.

It should have very little smoke. The “right color is light blue gray. Brown is typically from an old dry muffler packing more often seen on a car. Dark gray/black is too much fuel.

Check the color again

Xxxxx

Very responsive


With or without choke?

I saw your answer later in the post but just double checking.

xxxxx

just trying to get it to idle now, maybe I do need a smaller jet then a 480.. I'm thinking to rich right now.


Just reconfirming again

Does it idle at all?

Does the idle mix screw have any affect at all?

Again check float level. Too high is rich.

xxxxx

By the way, pilot jet is a 45


Good this is stock as I previously posted for you. Again since it starts easily with no choke it may be the proper size if not slightly large or have a high float level.

xxxxx

Went and test road it with factory 470 jet, choke and it runs great. No choke and it bogs down some but at high rpms it seems to keep up good.. I'm thinking it is lean.. but I'm no expert. Not a whole lot of smoke. But on choke the idle is much higher. It barely idles if at all without choke. Messed with the mixture screw quite a bit, its at least 2+ turns out right now running best. Throttle settles to idle slower then it should it seemsand not a whole lot of smoke compared to bigger jets I experimented with earlier.


Check for AIR LEAKS and fuel pump leak as previously mentioned by MOSH in post #10. You can replace the BLACK fuel pump VACUUM line with a CLEAR one. If you see fuel in it you pump is leaking.

xxxxx

I've replaced the plug, and added octane booster to a full tank if fuel with no improvement.


What color is the NEW plug now?

With no improvement in what exactly? This will not make a vehicle perform better, it is only to reduce DETONATION/PING.

Does it ping less with the octane booster?

xxxxx

Could sparkplug gap cause any of the problems I'm having,


Yes, check manual I gave you for the spec but I think it is around .022-.025, could be wrong though.

What plug is in it, brand and letters on side?

xxxxx

I bought some yamalube 2 stroker oil last time I was In the big city.


What ratio are you mixing it at?

xxxxx

Maybe I should add some higher organs fuel,


I’m assuming you mean OCTANE not ORGANS, What the heck are you guys making your gas out of, old body parts? Again octane won’t help performance. Do not increase octane if it does NOT detonate/ping.

Xxxxx

and reduce the jet size down to the 480 or 490 jet?


You said you had a 470 in it.

What is in it now?

Xxxxx

I also adjusted the floats some, the rejetting kit instructions said I could do so, so I took initiative (experimenting) by slightly bending the floats upwards allowing the bowl to fill a little more.


Higher or lower?

What affect this have if any?

Reset to factory spec or quit trying to jet it. This setting must be correct or you are wasting your time. Scratch that section off of your SIGMA NON FACTORY JETTING INSTRUCTIONS.

xxxxx

As far as jets go, I don't know how you guys determine sizes. But I ordered a jet kit from 6 sigma on eBay. company asked for what mods the bike had then sent me a jet kit specifically for the bike. Kit came with a 460mh jet, a 480mh jet, 490, and 500. Im guessing stock must be a 470.


Yes stock is 470 as you saw in my post.

Did jet kit come with a red and blue needle?

If so did you install it?

If it had one and you installed it remove it BEFORE doing any further jetting and shove it out of the way somewhere. DO NOT USE IT.

Xxxxx

SUMMARY

CARBURETOR - You might remove pilot and inspect both pilot and orig 470 main jet closely. Hold them up to a light and look thru them. If either looks “crusty” or has a white/yellow powdery look to the inside then they are still partially plugged. You must stick a similar size drill bit in them and spin them on the bit. This will help break loose the crust. Once clean look at pilot jet hole in carb for same thing, if it looks clear then clean again with carb cleaner, not brake cleaner, set float level to proper height reassemble with original 45 pilot and orig 470 main and orig needle and put needle in middle position and start from 0.

Install slide in carb and see if it feels loose. The slide to bore clearance should be very tight.

FUEL PUMP - Install clear vacuum line on fuel pump and check it for fuel.

AIR LEAKS - See MOSH post #10.

Tell us if it pings less with octane booster.

Tell us what gas oil ratio you now use.

[barnett468]

Hello

Some of my questions are repeats of ones that I originally asked that you did not answer, others are some questions asked by others but are still unanswered. You can reply to all in one post if you want, it doesn't matter either way.

[TRI-CYCLE]

It needs choke to start from cold

The temp in nodak always varies widely. Last time I ran the bike it was about 50 degrees out

Its most responsive with choke right now, but it idles higher then it should. When you blip throttle it takes a little longer to restabalize to idle I do believe (lean)

Without choke I could get if to idle for the most part after I had just ran it at higher rpms.

Did an air leak test with a can of carb cleaner, sprayed around the jug, intake, carb, and vac lines. Didn't vary rpms ar all

Pulled the new b8es NGK plug out after various riding rpms and it was black and slightly wet

Engine noise sounds like a clatter to me. But seems consistent. Octane hasn't changed it.

I run the fuel ratio at about a 32:1 with 91 octane

Main her is factory 470, pilot is 45 and needle clip is second notch from bottom

Float could be a little high. I haven't measured because I don't have a precise enough measuring tool. I'll have to check it asap

[TRI-CYCLE]

Can someone please answer, on the mixture screw, screwing it in would be more rich, and out would be more lean.. correct?

Walked into the garage to tinker on it some more. About 65 degrees. Fired first kick without choke. Idled for a minute. The withered out. Idles pretty well with choke. Bluish white smoke. Not an excessive amount though. Seemed pretty normal. Could be a little rich from out of adjustment floats probably

Had to shut er down when the cop pounded on the door about a noise complaint

[TRI-CYCLE]

May I add, the post above this one, when the bike fired first kick without choke. Before kicking it over I changed the needle clip position to middle notch.

Main-470
Pilot-45
Needle-center notch

[El Camexican]

Can someone please answer, on the mixture screw, screwing it in would be more rich, and out would be more lean.. correct?

Yes, it is an air screw. If it was a fuel screw it would be located past the slide and the opposite (in lean, out rich) would be true.

[Bryan Raffa]

no more than 2 turns out on that air screw..from Lightly seated..

[TRI-CYCLE]

Ok thank you

[Dirtcrasher]

Your crankcase might be full of old fuel and oil and your pipe and silencer are likley full of goo. If it seems to be running good take it for some good high RPM rips and get it good and hot. Expect lots of smoke. You may want to change your muffler packing soon as well.

If it still seems to be loading up with fuel after that you may have another problem besides the main jet size. The stock main jet may be too big to run perfectly, but that shouldn't cause raw fuel to blow out the pipe.

Oh, and BTW I think the air screw in that carb came with a blunt tip, so don't worry about that.

HEY!! We all need a bar-b-q starter :D

[barnett468]

Hello


It needs choke to start from cold, The temp in nodak always varies widely. Last time I ran the bike it was about 50 degrees out


Full or half choke?

xxxxx

Its most responsive with choke right now, but it idles higher then it should. When you blip throttle it takes a little longer to restabalize to idle I do believe (lean)

Without choke I could get if to idle for the most part after I had just ran it at higher rpms.

xxxxx

Did an air leak test with a can of carb cleaner, sprayed around the jug, intake, carb, and vac lines. Didn't vary rpms ar all


Does your carb cleaner say flammable on it? Most carb/brake cleaner is water base now and won’t burn. Do it with flammable cleaner.

xxxxx

Pulled the new b8es NGK plug out after various riding rpms and it was black and slightly wet


Too rich may be high float level as mentioned.

xxxxx

Engine noise sounds like a clatter to me. But seems consistent. Octane hasn't changed it.


Piston is likely hitting head or piston/cylinder clearance is too much or it partially seized then stuck rings to piston causing low compression.

Do a compression test.

Remove ex and carb and look at piston for damage.

Remove plug, bring piston up just before top dead center [check it with screw driver], take a thick piece of solder and stick it thru plug hole until it reaches cylinder then slowly kick over and remove solder. If it is less than .010 thick you have a head shape problem and it needs to be corrected.

xxxxx

I run the fuel ratio at about a 32:1 with 91 octane


This ratio will not make it smoke.

xxxxx

Main her is factory 470, pilot is 45 and needle clip is second notch from bottom


Good this is stock.

xxxxx

Float could be a little high. I haven't measured because I don't have a precise enough measuring tool. I'll have to check it asap


You don’t need a good measuring device, just a tape measure. You need to do this first before jetting.

31.3 MM OR 1 ¼” FROM CARB BASE.

CARB FLOAT SECTION 3-9
http://www.oscarmayer.net/atc/manuals/Yamaha/tri-z_250_servicemanual.pdf

xxxxx


Walked into the garage to tinker on it some more. About 65 degrees. Fired first kick without choke. Idled for a minute. The withered out.


Rich o pilot, mix screw and/or high float level

xxxxx

Idles pretty well with choke. Bluish white smoke. Not an excessive amount though. Seemed pretty normal. Could be a little rich from out of adjustment floats probably


NO, blue white smoke is OIL. Black smoke is too much gas.

Xxxxx

May I add, the post above this one, when the bike fired first kick without choke. Before kicking it over I changed the needle clip position to middle notch.


Shouldn’t matter too much for starting if it was only moved 1 position but starting with no choke when cold outside is too rich ie jetting or high float level.

Xxxxx

Have you had to add trans oil because it was low or is it currently low? It may be getting sucked into crankcase due to bad seal.


I think you need the following before changing jets.

1. Compression test

2. Check float level.

3. Redo exterior leak test.

4. Do a leak down test. A bad clutch side crank seal will cause many of the problems you are experiencing except for the rattle noise however if your seal is bad it can make your bike run lean which can cause it to seize and rattle.

[barnett468]

Hello


I forgot, replace the black vacuum line from the fuel pump with a clear one, if you see gas in it your pump is leaking gas into te engine creating a rich condition, very common problem. Fuel pump is rebuildable. See oem parts fiche and parts dealer in link below.


http://www.cmsnl.com/yamaha-ytz250n-1985_model9122/partslist/A-10.html#results

http://www.cmsnl.com/yamaha-ytz250n-1985_model9122/partslist/

[barnett468]

LEAK DOWN TEST VIDEO - If you have a leak and don't see it you must remove clutch cover and cdi cover etc to see crank seals. You can use vacuum and if it looses vacuum then pressurize it and spray with soapy water or just pressurize and use soapy water.

http://www.youtube.com/watch?v=zdq7NRcUIp8

[TRI-CYCLE]

Thanks for the great info. I will try all you said above. And answer accordingly.

I recently filled with trans oil, I've owned the bike for over a year, hardly put any hours on it, and never checked trans oil when purchased. So now that I know if was full a few weeks ago I'll check it again.