Tri-z falling flat on its face

[Rigaman]

Edit: It wasnt cutting out. It was the power band losing power, then hitting again. It felt like it was revving in neutral for a second almost. Like totally lost power in the high revs.

My 85 tri-z has been falling flat on its face. Only when I pin the throttle pretty fast. If I ease in the throttle, it doesnt happen. It seems to happen in just about every gear. Maybe not first or second, but definately 3 and up. around 1/2 to 3/4 throttle. In between half and full If I fan the throttle a bit, I can kind of get it to stop.

My tri-z is an 85. Stock carb and jets. Stock needle position. It has a 70mm piston. Dg pipe and silencer. It isnt sealed too well up on the head, and puffs smoke from the head, and spluge. I do have spluge on the mouth of my silencer after a ride too. Also, I dont have a good gasket between the silencer and pipe. So there is splooge all over there too. (just being thorough)

Stock reeds. K&N filter. No airbox lid. Yamalube 40:1 About 60 degrees last ride. Sea level.

If anyone can help diagnose this, it would be a big help. It runs and idles great. Has instant throttle response while sitting with no load. Even with load in first. I havent really slammed on the throttle though.

[willreed03]

Sounds like a jetting issue and it might be running lean...have you pulled the plug to see what it looks like? With a K&N filter and no lid and a DG pipe you should have at least jumped up 1 or 2 jet sizes on your main jet and possibly lowered the clip on the needle which raises the needle...

[El Camexican]

Clean your carb and check your float level before you change anything. Then make sure your fuel pump is working. If all that checks out you may have bad crank seal or an electrical issue.

[willreed03]

Agreed with what El Camexican said

[Rigaman]

My crank seal is ok. I am not loosing any gear oil. My carb is as clean as it gets, but I did mess with the float level when I cleaned it up a couple weeks ago. I never opened the tri-z up until the other day. The fuel pump is pumping great too. Maybe not great enough? But I have a clear line and can see it pumping.

I have an update. So. I opened up my carb today. The needle was set on the top notch. The leanest setting. It had full power, and really ripped at that setting. No pinging or popping. I dont think it is lean. Only fell on its face if I pinned it.

now. Before I read all of your comments, I changed my air filter to a uni filter. Put the needle one clip down, and put the air box lid on. It didnt have anywhere close to the power it should at that setting. It didnt bog, but it didnt hit the power band like it should. It just wasnt there.

I took the air box cap off, and it felt a little better, but was lacking power. Low end wasnt there at all. High end was blah.

SO. It seems that my carb settings I had were pretty good. I know these tri-z's are very rich from the factory, and alot of people have to go down a main even with lots of mods.

Since my needle is set so lean, do you think it is a good idea to try to go to a lower main and adjust the needle down? Or just leave it as it is?

I am thinking my float is the problem. This only really happens when I power shift through the gears, and really lay on the throttle. So it is not getting the gas it needs from the carb it sounds like. Its like the fuel pump isnt flowing enough gas to keep the level up when I nail the throttle. If I fan the throttle it gains back up.

[El Camexican]

Float height and proper cable function are the first steps to tuning. There is no point to doing ANYTHING else to the jets till this is right. Same goes for poor baffle packing and a leaky head connection.

Try trouble shooting in this order:

- Repack the muffler, use steel wool if you can’t find packing material
- Pull the pipe, clean it up and silicone it on for now.
- Check the plug gap
- Make sure your plug cap is tight on the coil wire
- Make sure the air filter is not over oiled
- Set the float height
- Make sure the cable is closing the carb slide properly at all steering positions and that it opens all the way
- Set your needle to the middle position and your air screw to 1.5 turns out.
- Start the trike and warm it up till it’s hot then set the air screw. If you can’t get it to idle off the choke and run right between ½ a turn and 2-1/2 turns out you need to change the pilot jet until it does.
- Once the pilot and air screw are sorted out take it for a ride and determine if the needle needs to be moved. If you are having to go to either extreme on the clip height you are likely off on your pilot or your main. The center and one notch either way are where you should be.
- Once you have 0 to ¾ throttle sorted out you can start tuning the main jet. Start rich and come down till you get rid of the top end bog. Once you get rid of it don’t keep going down.
- Once all this is done you can return to the air screw and start fine tuning.

It this does not work you have other problems.

[Micahdogg]

It will go WOT and run acceptible if you roll into the throttle, but not stab it? OR can it not ever go WOT anymore? What does the plug look like?

[Rigaman]

ya. It can go WOT if I ease into it. Just when I punch it it falls on its face, then recovers. But then I gotta shift again, and it does it again.. Just gets annoying. Plug looks a little dark, but not wet.

Slide closes properly. And the silencer is brand new with about 3 hours on it.

It feels like the fuel pump isnt keeping the carb filled fast enough when I pin it real hard. Or the float height. Idles great. I while its in neutral, I can slam the throttle on and it revs perfect, and drops right back to a perfect idle. Air screw is set right. It is about as fine tuned as I have seen any z. Just this one little issue.

[pcs]

my 85 z is/was 100% bone stock and when i removed the lid off air box and plug out of the stock silencer it was running lean at WOT according to the plug. went up one size on the main and the plug is back to the normal color. i know some say the 85 is a bit on the rich side from the factory but im just going of the plug readings. im 600ft above sea level and riding around 70F. is there any difference if your gas tank is full? fluid pumps work harder to maintain flow rate when there is low suction pressure, ie low tank level. the higher level of fuel above the pump makes it easier for the pump to work. maybe you can hook up a pressure gauge to see what you are getting on the discharge side. i would say with a pump that is >25yrs old it might be time for a rebuild.

[volfan537240]

If the head gasket is leaking, fix that first. #1 way to kill a 2 stroke is with a air leak anywhere on the motor.

[Rigaman]

PCS, thats kind of nice to hear. Everyone tells me the Z is very rich stock. So maybe I need to go up a main, and lower my needle back to the center.

Ya. I think it might be time for a fuel pump rebuild. I have a couple extra fuel pumps, so I can rebuild one. Anyone know a good place to get a fuel pump rebuild kit? I heard snowbobile places have them pretty cheap. I just need to know what model to look up.

Volfan
It is not leaking from my head gasket or base gasket. Just the exhaust pipe isnt fully sealed up where it meets the head.

[volfan537240]

I thought you said in the first post that it was leaking

[Rigaman]

Oh. No. I meant the exhaust wasnt fully sealed up. Ya. If my head gasket was leaking I would definitely have a problem.

Thanks for your reply though. I appreciate you taking the time to help me out.

Anyone know where to get a replacement choke for the tri-z carb? I cant find one. What model is it? A VM26? VM something?

[Rigaman]

Ok guys. I diagnosed it wrong. When I found out about the problem, my friend was riding it. I took it out yesterday and really opened it up, and I felt something totally different.

When the power band hits, it hits semi hard, then drops out, and hits back again at around 3/4 to full. The revs keep going up. It doesnt cut out or anything.. The motor keeps revving, but the power gets lost and then kicks back in.

It is very annoying. I know the power band has to do with alot of different variables. Anyone experienced this?

[El Camexican]

That sounds like a needle adjustment issue. Try going richer first (lower the clip 1 notch) If it gets worse then try raising the clip. It sounds like your main jet is close or good, but if you end up with the needle all the way in one direction you should change the main accordingly. I know its a PITA and you end up with an expensive brass collection, but this is the only way to get the jetting right.

[Kfx-xc-racer88]

I only read half of your post!! SOUNDS LIKE YOUR CLUTCH IS SLIPPING??

[Rigaman]

Ya. My needle is all the way lean. And if I put it down one clip, it bogs a little.

I think my dg pipe is making it lack performance too. Plus. My silencer isnt sealed up to the pipe. I need to get a gasket for it. My pipe isnt fully sealed up at the spigot on the head too. Maybe that is hurting my performance too.

[Kfx-xc-racer88]

Your clutch is slipping!!!!!

[Rigaman]

I dont think my clutch is slipping. When I said it is like it feels like it is revving out in neutral, I meant it doesnt bog, but the power doesnt hit like it should. I will check my clutch though.

[Kfx-xc-racer88]

I know by the sound of you explaination, its not bogging because the clutch starts to slip so the revs will rev out until you back of the throttle enough for the plates to grip again.
thats why it revs out but not the power hit you expect and in the higher gears its worse as the plates are struggling to maintain the drive under more strain... check the clutch plates and springs?
as soon as i read your post i knew it was your clutch, get it on a dyno and get the carb jetted and set up properly.

[Rigaman]

Ya. I put a new bigger carb on it, and now it is just bogging. So I will go back to my old carb and check my clutch. I will swap clutches and let you know what happens.

Ya. It was making me crazy, cause every time I told people what was happening, they assumed when I lost power, the engine lost revs. But the engine reved all the way through. Didnt miss a beat. But As soon as I hit the power band, it looses it. It isnt a violent slip and grab though. It just doesnt feel like it is slipping. But it makes sense that thats what it could be. I hope it is that I want my Z to rip.

[El Camexican]

Rigman,

If you are at max lean on your needle please go down one size on your main and set the needle at the second notch from the top (one from max lean) as a starting point. See if that helps. As far as clutch slippage goes, yes it happens in the top end more so than at the bottom and is exacerbated by going uphill, but the symptoms should not include a “bog” unless the engine zings up, the trike slows down, the plates heat up, and then lock at a speed that is too slow for the engine to pull. If you feel that this might be the issue then test your jets in 2nd or third gear and not in 5th as the engine should be able to easily pull in those gears. Also, is it hard to find neutral on your trike? Typically if the clutch is fried it should be hard to find.

[Micahdogg]

This is starting to sound like a mechanical problem that you won't be able to jet away. You probably need to give everything a good once over and make sure it's not a punctured carb boot or something that is making it act so erratically.