Im "throwing in the towel" on this Tri Z

[Racer-X]

I hate to say it but I may have to bite the bullet and take this machine to the shop and pay (money that I don't have) for them to figure it out. I don't understand why it starts for a minute or two but only if its cold and its the very 1st attempt at starting it for the day. It starts right up but runs sorta boggy (if I give it throttle it wont rev up high at all and instead it boggs down) and I have to blip the throttle a little bit just to keep it idleling but it eventually gets slower and slower and boggs out completely. Then after that it wont start again? Not even with a shot of starting fluid even though it was just running for a minute. But it will start tomorrow and do the same thing. It will run like crap for a minute, just Bogg out, and wont start again? I bought it a few years ago, put plenty of miles on it, and it ran ok. It just smoked more than its supposed to which I assumed was due to an old worn out piston and jug. Then it started doing what's its doing now. I figured it needed rebuilt or reeds or something. so now I finally got it all back together after having it bored .040 over. (fyi don't bore a tri z jug to .030 because for some reason nobody makes rings that size? You can get .010, .020, and .040 only) Its got a new air filter, carb is squeaky clean, new reeds, new piston and rings, plug, ect.... The compression gauge is reading 155psi. the spark plug is definetly sparking. I even tried another plug just in case and they both spark fine. So it seems I have fuel, air, and spark but its not running? I thought maybe the stator but its sparking fine. And I also thought maybe the fuel pump but why would it not start with a shot of starting fluid and why does it pump fuel for a minute or 2 and then stop? With starting fluid sprayed in the cylinder it should at least run for one second or 2 even if the carburetor was completely missing and it literally had no fuel in the tank right? It doesn't even try to start. It doesn't even hiccup? Once it runs for a minute and boggs out its done for the day. I could kick it 100 times and absolutely nothing happens? Maybe I'll try gravity feeding the carb and eliminate the possible faulty fuel pump completely. But the possible bad fuel pump doesn't explain why it doesn't show any signs of life with a shot of gogo juice.
I just don't get it?
Any thoughts?

[muthey]

I hate to say it but tear the cylinder off, and check the rings, I had mine do the exact same thing and found out that one of the rings had bent a corner at the opening. I could get a good read out on a compression gauge but it would do the exact same thing yours is doing.

[lndy650]

what did your reeds look like when you rebuilt it? i would try gravity feeding the carb see if that helps. sounds like it could also be a sheered flywheel key or another timing issue.

[Racer-X]

Well, when I was installing the jug I was able to look in through the intake port and see that the rings where exactly centered in their correct location on the pins. One actually moved just a little bit and the jug wouldn't slide on. I went in through the intake port with a screwdriver and spun the ring a little bit to the correct position and the jug slid right on. Then when I pumped the kick starter and cycled the engine before I put the top onto the jug it sounded and felt smooth as butter. Also I was having this exact same issue before I rebuilt it with the old piston and rings. It quit running and was doing the same thing. That's the whole reason I rebuilt the top end in the first place.

[Racer-X]

The old reeds didn't look bad. One of them had a small area on the side where the reed wasn't touching the cage but not by much at all. Both the old and new reeds are Boyesen. I not familiar with what exactly a flywheel key is or how it could be out of time. Ill look into it. But yeah, I'll try bypassing the fuel pump next.

[lndy650]

does it backfire or kick back on your foot when you try starting it? the flywheel is behind the cover on the shifter side. theres a sensor that picks up the position of the crankshaft and if the keyway on the crankshaft is sheered off it will fire at the wrong time and will pop and backfire but usually wont run. only other thing i can think of is a weak cdi they can play all sorts of games. if you have a multimeter i can get the specs you need to test the electrical. dont give up buddy youll get it running.

[jeswinehart]

It sounds like a crank seal problem imo. Doing a leak down test is rather simple + cost hardly nothing.

john

[Imdone]

Classic symptom of a failing canooter valve. Unfortunately an NOS one is extremely hard to find. Best of luck in your search.

[atc300r]

X2 on crank seals.Also sounds to me like your crank case has to much gas in it and its flooding it out.

[fieldy]

Squeaky clean carb, whats that mean? When you are kicking 100 times and no fire does it have spark then? If it always has a blue spark then cdi should be ok. Yellow/orange spark-bad, electrical. Can we get a plug picture? The timing and flywheel need verified as mentioned, probably need a puller and a gasket. If electrical is shotty can a YZ ignition be found today? I know, no head light......honestly don't know on Yamaha. Yes gravity feed the carburetor!
I would wait and check a few of these things before worrying to much. 100% leakdown test it or the shop will be getting in your pay. I agree you will get it, just gonna take some garage time. Working on em is the fun part anyway!

[ironchop]

.... (fyi don't bore a tri z jug to .030 because for some reason nobody makes rings that size? You can get .010, .020, and .040 only).....

That's because metric pistons come in oversize increments of 1/4mm (.25mm), 1/2mm (.50mm) and 1mm

.25mm = .0098 inches so it rounds up to .010

.50mm = .0196 inches , rounds up to .020

1mm = .0393 , rounds up to .040

To convert mm to inches, divide mm by 25.4

To convert inches to mm, multiply inches (in decimal format) by 25.4

Sent from my Z958 using Tapatalk

[lndy650]

i was thinking the possibility of crank seals but for them to be bad enough to where it wont stay running there would be gas in the transmission oil and probably gas/oil in the flywheel cover. so i would also look for drainage around the crank seal when checking the flywheel and see if you can smell gas in the transmission oil.

[Racer-X]

Aha, the good ol' canooter valve. Why didn't I think of that sooner. I think I have a new one somewhere around here. Maybe its with my pipe stretcher hahaha. I think you guys may be onto something the crankseal . If it was electrical I think it would be broke all the time not just a minute after running. And it does start right up after it has sat for a long time and aired out. So maybe when it starts for the 1st time the bad crank seal is gradually building up too much air or oil and eventually screwing up the air/fuel mixture to the point it cant run anymore.
I'll drain the oil and inspect it and I'll try to rig up something for a leak down test or blow some air in there once I have the side cover off and can listen to see if there's air coming from the actual crank seal.
Why am I always fixing stuff? I just want to ride!

[jeswinehart]

http://www.3wheelerworld.com/showthr...leak+down+test

http://www.3wheelerworld.com/showthr...leak+down+test

Best to do it right,,, the first time.

[schlepp29]

My 250r did the same thing and it ended up being the secondary coil. A stupid 50 dollar part was all it was. But all the other stuff these guys are saying is most definitely possible as well. When my r was acting up we did everything to it, leak down, top end ,carburater ,reeds and spark plug wire and boot. I hope you figure it out. Good luck