Anyone wanna show me how to rebuild a 2 stroke?

[Sheep Dags]

Hey whats up,

I've got a wicked TZR250, which is the most fun ever... when it starts! - that's the problem!
Yea it won't start! I've owned an NSR250 before this one so I know a bit, but have never taken a look inside the engine and would love it if someone with experience could teach me some things. (such as rebuilding it!)
So here's the background:
Since i bought it, it was harder and harder to start (when cold), now I have to push start it down a steep hill every time before it will start. The plugs are fine, the battery is fine, the fuel flow is fine, the compression is fine. All of that is sweet - and no, it's not siezed. It seems as though all it needs to get going is a lot of revs - hence the steep hill, kicking just doesn't cut the mustard. I've had Dave look at it and he said apart from pulling the engine apart and having a look inside, nothing's wrong with it. and the guys at spectrum (barrys point rd, takapuna) said the same thing. I really want to get it sorted out before summer, cause i wanna do heaps of riding, and i'm afraid that because I can't start it for shit, I've just left it for a few months and don't even want to tryand push it down the hill cause if it gets to the bottom without starting, i'm fucked!

Ok so it is a hell of a bitch to start from cold. When warm, it will start first kick, every time. But if I leave the bike for at least half an hour, it needs a push start. And pretty much the longer i leave it, the faster i need to run with it before it will start.

That's why i'm thinking it's something to do with inside the engine - maybe the pistons are worn or something, i dunno, i don't really know too much. What i do know is that it got new rings a couple of years ago, but not new pistons.

If someone could help me with this I'd be so stoked, I'd need a place to store it while it was being fixed, cause i don't have a garage to store it, so if someone has some spare garage space, or a workshop or something, and is keen to help me out it'd be much appreciated. And also, if I were to rebuild the engine, does anyone know of a place i can get cheap pistons and rings etc.

i don't mind paying for your time, since i will be learning heaps at the same time, i just can't afford shop rates.

hope to hear from someone soon,
Cheers,
- Mike

[FROSTY:Me]

I"m right away suss on your power valves.
Id haul the heads and barrels off and take a look.
You could need.-3x power valve seals.
1x head gasket and 1x base gasket.
I could go on for pages and pages about what to do but basicly I'd give her a big clean up inside

[Two Smoker]

Ive had that problem, check the choke cable (ie whether or not it is broken) if its sweet, make sure you use no throttle when kicking, when it starts dont touch the throttle until the revs come up..... How many kays has it done??? that will be an indicator too whether it needs a rebuild or not

[DEATH_INC.]

Two strokes are pretty simple,if the compressions good then the rings/pistons/crankseals ect should be ok.I'm with 2smoker,check the basics,and check the reed valves if it has them.
It really sounds like lack of compression,when was it checked and what was it?

[Fluffy Cat]

Ok my history>I have 2 two strokes at present an NSR MC21 and an aprillia RS 250 I have spent most of my biking life on two stroke race reps thats twenty years.Next it is very hard to diagnose these sort of probs over the internet but here goes.First what sort of tzr early model or later.How long have you had the bike(whats it's history).From what you say it could be any fo hundreds of probs from simple ie cheap fix to whey expensive!.So lets try simple first.Check battery check battery conections put in new plugs check spark check plug caps clean plug caps check coil connectins and eart points on frame clean them with file or similar check and clean all connections All connections.Power valves,well they could be seized but the bike should still start even if they are do they cycle when you turn on the bike do they move when the bike is running try reving till they move do they move together?.Take carbs off dismantle carbs are they clean any grunge inside use air gun to clean out jets do not use carb cleaner this will damage any rubber seals in the carb body check needles are in matching clips put back together check reed blocks and reed petals for damage.Now expensive check if you can cylinder pressures remove heads remove cylinders check for wear check pistons for wear replace piston rings piston and little end as standard.If clinder is worn replate or replace if earlier model re-hone or re-bore clean out carbon build up around power valves.Do the simple first!.I don't know the power valve check for the tzr so try searching on line.If i have missed anything hopefuly someone else will post.Let us know what you decide to do and how it goes.

[Posh Tourer :P]

I agree. It doesnt sound like you have experienced any problems while running, only starting. That should rule out powervalves, and worn piston problems are ruled out by good compression.

Try to make sure your choke cable is adjusted properly, and also get your idle speed correct. The beemer was a touch too low and was an absolute bitch to start when it was cold ie left outside for 6-8 hours. Up the idle speed, and it was much easier to start. Also, check your starting technique. Kicki it a bit, take the plug out and if you can see wetness on it, it is flooded, and you need to investigate your choke settings. Also it may be that your float levels are a bit low and you are running it too lean. Make sure they are at recommended levels.

Do all that first, *then* if it still doesnt work, look at a rebuild.

[Racey Rider]

Since i bought it, it was harder and harder to start (when cold), now I have to push start it down a steep hill every time before it will start. .... kicking just doesn't cut the mustard.
... it is a hell of a bitch to start from cold. When warm, it will start first kick, every time. But if I leave the bike for at least half an hour, it needs a push start. And pretty much the longer i leave it, the faster i need to run with it before it will start.
- Mike

I had the same thing with my KR1.
I changed to 91 octane which fixed the problem. Now it starts fine from cold,,(most of the time)!

[Sheep Dags]

thank for the replys guys,

i'm pretty sure the choke is working properly, cause once it is started, if i switch the choke off the revs drop right down... so assuming it works. also, someone was saying about the idle speed - it idles at around 1.5 is that too low? also i heard a good way to check if you're runnign to lean or too rich is if you close the throttle and the revs fall below idle and come back up - and vice versa. well the revs fall to about 1, then come back up a few seconds later. could this be part of the problem?

i really need someone to show me how to take things apart etc, as im not confident to do it by myself, in case i fluff something up. - and i dont even know what a lot of things look like - such as power valves

- i could try to switch to 91 fuel, that might work.

oh and by the way, the power valves make a sound when i turn the key on, but again, im not sure if this could be part of the problem as i dont know what sounds they are supposed to make etc etc. - as far as i know they cuold be sounding wrong


p.s. it is a 1992 model

[MrMelon]

That sound the power valves make when you start it up is normal. That's just them opening and closing. And when we had the fairings off we could see they were getting opened and closed properly. Once it's started it runs fine, so I don't think the powervalves are the problem.

From what I've found normal idle speed on a tzr 3xv is 1300rpm, and mine's pretty happy to idle there.

[Posh Tourer :P]

You might well be running too lean. Do you have a manual / specs for carb float levels?

[Motu]

As well as compression you need suck - the two don't necessarily go together,put a vacuum gauge in the intake somewhere and see how much you have on cranking (kick,letrik,whatever) crank seals could be stuffed.