Honda ATV Forum banner
1 - 20 of 28 Posts

· Registered
Joined
·
1,203 Posts
Discussion Starter · #1 ·
Well I figured I didn't have enough projects to work on, so I added another one. Picked up a 2002 Yamaha PW80 over the weekend. My first 2 stroke!! I couldn't pass up the deal. $250!!

I decided to dive right into the motor. (It really only took about 25 min to have the motor completely out lol) The guy who I bought it from claims it has a brand new top end, but I really doubt it. It has low compression and doesn't run very well.

I am extremely fascinated by how the 2 strokes work. If anyone has any pointers on 2 strokes, please chime in. I'm always open to new ideas and suggestions.
 

Attachments

· Premium Member
Joined
·
5,960 Posts
Two-strokes are cheap and easy to fix thats for sure. It looks like you got a great deal on that one!

Two-strokes need good tight crankshaft bearings and crank seals, a decent piston/skirts to bore clearance (not sloppy with collapsed skirts), good piston rings and in your case, those reed valves need to fit and seal on the seats of the reed block well when closed. Resist any temptations you might have about bending those stock reed stop tabs up for increased opening and more intake flow... they'll bend or break on ya. Generally a good straight cylinder with a new piston & rings cures most of them up, on the cheap. I always run 32:1 oil ratios in two strokes as well, it saves on jugs/pistons and rod bearings replacements. If oil injected I crank up the oil pump delivery rate and regardless of how the oil is added to the fuel, run some good quality smokeless syn or semi-syn in them. Final tip: let the piston and jug get hot before revving the motor (piston skirts get hammered down if ya don't) or riding the bike.

It'll be fun.
 

· Registered
Joined
·
1,203 Posts
Discussion Starter · #3 ·
Thanks for the reply. The gentleman before me removed the Oil Injection system, he said to just mix the gas and oil in the main gas tank. He said he has blown too many bikes because of the oil injection failing. I don't know what kind of fuel he used but when the bike is running it smells like sweet candy.

Do those reeds look good to you?? I have no idea. I'll have to go do some research.

I appreciate the advice
 

· Premium Member
Joined
·
5,960 Posts
Smells like candy ehh? It might have Klotz 2-stroke oil mixed with the gas, that stuff smells really different.

The reeds & seats can generally be checked using a flashlight shined at them from the back of the reed block. You might see very narrow slivers of light getting past the reed petals or none at all. In either case they are probably fine... look for worn out seats or bent/cracked/chipped petals or embedded debris in the seats holding them open, if any of the gaps look excessive. The FSM might have better information on checking those particular reeds.

I assume the oil injection pump was removed and blocked off, or the driven pump gear taken out of the motor? Else a dry oil pump will seize up.

Its good that the motor runs, can't be very much it needs if it still idles OK. Ya gonna keep it around for a while and ride it after its back together?
 

· Premium Member
Joined
·
5,072 Posts
You’ll love this build, quick, cheap and so easy! As retro said, piston rings and a good clean up usually cures all on a two stoke. A friend of mine had one of these when we were kids, they appear to be bombproof!
 
  • Like
Reactions: XplicitRacing6

· Registered
Joined
·
1,203 Posts
Discussion Starter · #6 ·
Smells like candy ehh? It might have Klotz 2-stroke oil mixed with the gas, that stuff smells really different.

The reeds & seats can generally be checked using a flashlight shined at them from the back of the reed block. You might see very narrow slivers of light getting past the reed petals or none at all. In either case they are probably fine... look for worn out seats or bent/cracked/chipped petals or embedded debris in the seats holding them open, if any of the gaps look excessive. The FSM might have better information on checking those particular reeds.

I assume the oil injection pump was removed and blocked off, or the driven pump gear taken out of the motor? Else a dry oil pump will seize up.

Its good that the motor runs, can't be very much it needs if it still idles OK. Ya gonna keep it around for a while and ride it after its back together?
I believe that the oil tank is still connected to the motor, I'm not 100% sure.

The reeds are like the 2 stroke version of the valves right??

It was idling extremely high. I found a massive vacuum leak in the carb, and the jets had a ton of dirt in them.

I only got it into 3rd gear before It really started to bog. She cooks for a little 80cc. The power band is something I am going to need to get used too.

I plan to keep it. It fits me perfect for riding around in the pits at the races.
 
  • Like
Reactions: retro

· Registered
Joined
·
1,203 Posts
Discussion Starter · #7 ·
You’ll love this build, quick, cheap and so easy! As retro said, piston rings and a good clean up usually cures all on a two stoke. A friend of mine had one of these when we were kids, they appear to be bombproof!
I have seen a full grown men ride them around at the races!! They are a pretty big bike for how small the engine is. They are perfect bikes to throw in the trailer (Literally)

I believe I got a great deal. The guy put on all new plastics. New front tire. New twist throttle.
 
  • Like
Reactions: retro

· Registered
Joined
·
8,309 Posts
I wouldn't suggest mixing the fuel in the tank, get a separate fuel can JUST for this bike or other two strokes you have(weed wacker/chain saw ect.
reason I don't like mixing in tank is its a LOT harder to SHAKE the tank to get a good mix, as to a fuel can, where you can go ape crap crazy shaking if you like
I second ONLY run good two cycle oil too, and make sure its temp rated, NOT a real issue for some folks, but even some top shelf .sny. two cycle oil is NOT made to be used below like 35 degree's, some start to not mix well, More an issue for those running chain saws in COLD weather or snowmobiles, than bikes, but HEY I used to ride my MX bikes all yr here even in up to 2 ft of snow, and on ice(studded tires)
so you don't want a melt down due to wrong 2 cycle oil !

as for fuel, odds are plain Jane 87 octane will be just fine, this ain't no race motor ,
I personally run super in all my toys, just due to more places here sell it NON ethanol at the pump, and well, my friends MAKE fuel in refinery's and tell me it has better cleaning agents and well, just a cleaner fuel?
plus when it sits a while, ALL fuel drops octane, so starting off higher keeps it higher longer,
I DO NOT run it expecting any POWER BOOST< just for above reasons
have never blow a moot on it yet, and many have 20+ yrs on them problem free running, so works for me LOL
 

· Registered
Joined
·
1,203 Posts
Discussion Starter · #9 ·
Thanks for the reply. I see what you mean by not mixing it in the tank. I appreciate the advice. Hopefully she will be good to me :)
 

· Registered
Joined
·
1,203 Posts
Discussion Starter · #11 ·
That's sweet, I need to get a little backyard racer.

Rob
Thanks!! I really think I got a good deal on it. It's going to be perfect for what I need. The only thing that I have to complain about it is that there is no exhaust...... Way to loud
 

· Premium Member
Joined
·
5,960 Posts
If you can get the exhaust system back to stock it shouldn't be too bad. You might want to add on a silencer though, if using it as a stop&go pit bike.

My neighbor had a reed-valved Yammie 100 when I was an early teenager growing up. I remember how much more torquey his motor was than my little Kawasakis... Mine had all or nothing powerbands at high RPMs only, while his would pull decent right off the bottom. The reed valves make a big difference at low RPMs and his bike never seemed to break down... while mine was blown up and torn apart for cranks or pistons at least twice every year! Like SamUK said, Yammies seem to be long lasting, very reliable motors!

I learned to run 32:1 premix ratios in all of my air cooled 2 strokes no matter the oil quality. Nowadays the EPA mandates minimum oil consumption guidelines that the manufacturers are forced into, so first thing ya gotta do is correct that nonsense. There are many good oils to choose from that work great at 32:1 ratio available nowadays... to name just a few random ones in no particular order: Yamalube actually has one that works very well at 32:1, though it may be a bit pricey, Maxima K2 is pretty decent, Schneiders is great stuff (both full syn 9000 & the standard blend), Belray, makes one or two that are decent, Red armor is a good one and there are several others that are low/no carbon buildup oils. It really boils down to whats available in your area at a decent price nowadays, because there are so many good 2-stroke oils to choose from.

I like working on and riding two-strokes. This is a fun thread!
 

· Registered
Joined
·
1,203 Posts
Discussion Starter · #13 ·
Thanks for the great info! I really don't mind loud bikes...... but for just riding around in the pits, it's going to be too much.

Where is a good place to start searching for a silencer/ exhaust?? Ebay? Craigslist maybe? i just messaged the gentleman that I bought it from to see what 2 stroke oil he used.

Retro: I didn't even know that may different types of 2 stroke oil existed :grin

If it was your own bike what would you run??

I really enjoy this thread too. This bike was extremely simple to work on. Too very little effort to get the motor out. I think everyone should own a Pit Bike!
 
  • Like
Reactions: retro

· Registered
Joined
·
8,309 Posts
HAHA< I wish they never switched over to 4 strokes in dirt bikes, or at least not as many as they did, emissions came a LONG way on 2 strokes, I think they jumped the gun to make EPA happy yrs back
and doing so drove the costs of bikes up thru the roof, and took a TON of folks out of being able to work on things them self
2 strokes are simple to work on , and WAY cheaper too
and one well taken care up will last almost as long between motor work

as for getting this bike quieter, I would think it originally came with a rather quiet exhaust, due to its a kids bike
and I bet it came with a spark arrester too, something you might really want to have on it about places that have fuel and other flammable things, or plan to ever ride it LEGALLY on an trail system
many add one mufflers/exhaust silencers have them as an option !
 

· Premium Member
Joined
·
5,960 Posts
Thanks for the great info! I really don't mind loud bikes...... but for just riding around in the pits, it's going to be too much.

Where is a good place to start searching for a silencer/ exhaust?? Ebay? Craigslist maybe? i just messaged the gentleman that I bought it from to see what 2 stroke oil he used.

Retro: I didn't even know that may different types of 2 stroke oil existed :grin

If it was your own bike what would you run??

I really enjoy this thread too. This bike was extremely simple to work on. Too very little effort to get the motor out. I think everyone should own a Pit Bike!
I have no other ideas (other than ebay) where you can find exhaust parts, except I know someone who runs a salvage business. What year is it?

As far as oil goes... run what ya want and can afford to buy where you like to shop. I'm afraid if I mention anything about which brands of oil I buy, I might start an oil (arguments) derailing... and ruin your thread! LOL
 

· Registered
Joined
·
1,759 Posts
You may consider increasing the main jet to the next size bigger. Now that oil is in the fuel it is more viscous (thicker). You don't want to seize the engine because it wasn't rejetted. I think they were rich from the factory though so it may not be an issue.
 

· Registered
Joined
·
1,203 Posts
Discussion Starter · #18 ·
You may consider increasing the main jet to the next size bigger. Now that oil is in the fuel it is more viscous (thicker). You don't want to seize the engine because it wasn't rejetted. I think they were rich from the factory though so it may not be an issue.
When it is running it seems to be smoking pretty good. I'm really not worried about that. But thanks for the good idea. I'll keep that in mind.
 

· Registered
Joined
·
8,309 Posts
2 strokes are supposed to smoke, and at start up many times they smoke a LOT more than after things warm up
spark plugs are STILL cheaper than top ends, so I'd rather run extra oil in fuel/mix, than go light
all the more so for breaking in a top end, I always run first tank of fuel with a heavier mix of 2 cycle to fuel just for break in!
 
1 - 20 of 28 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top