1998 Yamaha PW80

[JWC86]

Traded a guy some gun powder for this 98 pw80 today.

My oldest daughter has been begging me for a dirt bike and this deal was too good to pass up.

Needs some work which is perfect because I’ve been wanting another project.

The good: starts and runs really well and all the important things seem ok.

The bad:

Needs a throttle cable

The head pipe heat shield is missing and it’s missing the muffler all together…

Missing the kickstand:

Chain adjusters are cobbled up:

Spark plug boot probably needs replaced

Steering head bolt washer doesn’t look OEM or really up to the task

Thats what I can see from my quick 5min inspection, me and my daughters will tear into it tomorrow and see what surprises it has for us.

Plan is to take care of what needs taken care of for now. Then over the winter we might tear it down and refresh it a bit.

 

[JWC86]

Small update:

The kids(and wife) really wanted to ride the "new" bike yesterday but I wanted to have a quick check over first.
I really wish I would have taken some pictures along the way but I was in a time crunch and enjoying having the kids "help" me.

We pulled the plastic off and the airbox and started by just giving everything a good scrub to get years of neglect off.

Opening up the airbox I found a filter that actually didn't look terrible, looks like its no more than 10 years old and wasn't complete plugged with filth. The airbox itself was packed with dirt and dried filter oil.

Got it back together and went out for a ride. Not running great but decent enough for the girls to try it out.
Here is my oldest, she had a blast on it and can't wait to go again.

Now that I've done a better inspection here is my updated list:

-Chain and sprockets
-Air Filter
-Throttle Cable
-Grips
-Kick Stand
-Kick Starter is floppy
-New reeds
-Front wheel bearings
-Front brake lever
-Muffler
-Head pipe heat shield
-Chain adjusters need to be replaced
-Check spokes(Back wheel is missing one)
-Clean Carb (possible rebuild)
-Air box attachment brackets are broke
-Seat bolt is buggered up
-Compression check
-Front brakes stick
-Spark plug end

Overall it seems the main components are good, just lots of small things from years of neglect.

I'll be sure to include more pictures moving forward.

Edit: Forgot to mention, I did a oil change when we got back from riding, perhaps that goes without saying since we are BITOG's.

 

[Alain2]

Is the oil pump still present and running?

 

[JWC86]

Is the oil pump still present and running?

It is still on the bike and appears to be working.

 

[cpayne5]

These little PW80s are great little bikes. I moved my boy up to one from a Honda 50 a couple years ago. He's now racing 65s. We still have the PW and he rips it occasionally.

One of the best mods you can do is to pull the rubber snorkel off the airbox. These PW80s have a rich bog at higher rpm. There is also a washer in the exhaust from the factory that restricts flow. May already be long gone, though.

 

[JWC86]

These little PW80s are great little bikes. I moved my boy up to one from a Honda 50 a couple years ago. He's now racing 65s. We still have the PW and he rips it occasionally.

One of the best mods you can do is to pull the rubber snorkel off the airbox. These PW80s have a rich bog at higher rpm. There is also a washer in the exhaust from the factory that restricts flow. May already be long gone, though.

Awesome!

Yes I'm going to have a look at the exhaust and see if the restrictor washer is still in or not. I think I'll leave the air box snorkel for now since the girls are brand new to this.

 

[Alain2]

These small Yamaha 2 stroke are rev limited, in part, by exhaust, if you open the exhaust make sure you put a bigger main jet to limit the engine. The restriction in the exhaust also increases cylinder compression and mid range torque. Your best bet is stock intake and exhaust with genuine Mikuni jets. Once the bike is proven reliable then you can start playing with intake/exhaust/jetting. You can also run 100:1 fuel until the pump is confirmed, quality oil will save your engine if the pump is kaput. If the pump works good you will have a bit of safety smoke!

 

[JWC86]

These small Yamaha 2 stroke are rev limited, in part, by exhaust, if you open the exhaust make sure you put a bigger main jet to limit the engine. The restriction in the exhaust also increases cylinder compression and mid range torque. Your best bet is stock intake and exhaust with genuine Mikuni jets. Once the bike is proven reliable then you can start playing with intake/exhaust/jetting. You can also run 100:1 fuel until the pump is confirmed, quality oil will save your engine if the pump is kaput. If the pump works good you will have a bit of safety smoke!

That's pretty much the plan for now. I'm leaving the intake stock and have a good condition used silencer on the way. I have a carb rebuild kit coming also that has all the oem size jets. New set of reeds also just because they are cheap and then it will be all fresh other than the top end.

There is oil in the hose and some blue smoke so I think it's working. I plan to check the pump stroke throw with OEM specs also.

I want to check compression but my tester grew legs...

 

[wpod]

Cute !

 

[thastinger]

You must have had some extra Retumbo

 

[JWC86]

You must have had some extra Retumbo

H1000, H4350 and Varget.

 

[paulo57509]

IMO, little kids are naturals with motorbikes and dogs.

 

[JWC86]

Still waiting on a bunch of parts but the throttle cable came in so I went about replacing it.

Currently the throttle is very hard to twist, my 6 year old can't even do it. the current cable looks like this:

So easy fix right? Well the PW80 has a 4 piece cable design: The cable shown that goes from the twist grip, then it goes into a splitter box where it splits into 2 cables, one cable to the slide on the carb and one cable to the oil pump that adjust how much oil is injected depending on throttle position.

My plan was to replace the main cable from the grip to the splitter since it clearly needed to be replace and then I would inspect the splitter box and other cables from there. All 4 parts cost around $100 I believe so I didn't want to replace them if not needed.

Turns out someone replaced the whole thing with aftermarket cables and splitter which is not compatible with any of the OEM cables. I understand why someone might do this as I looked it up and this sells for $15 but the quality of the splitter is poor, has a few cracks in it so I will just replace all of the cables and splitter with the OEM parts.

I also inspected the choke cable and its very sticky, its very slow to let the choke release and sometimes doesn't release it fully. I will replace it also.

Hope to have more updates soon.

 

[repairman54]

2x on OEM cables. I've never had good luck with aftermarket cable quality or fitment.

 

[JWC86]

2x on OEM cables. I've never had good luck with aftermarket cable quality or fitment.

I agree, called today and ordered all the OEM cables. The splitter was back ordered until Aug 14th however which is lame.

 

[JWC86]

We got parts

Everything came in except the connector for the throttle cables, handle bars and front tire. Lots here to get me started thou.

I needed a better way to hold the bike so I could drop the engine since this bike doesn’t have a frame under the motor.

I threw together this wheel chock in 10min with some scrap 2x4s I had.

That’s it for now. Hopefully next time will be a actual update where some work on the bike will get done…

 

[JWC86]

I'm going to pull the motor out so I have better access to change the reeds and inspect the injection oil pump.

Muffler needs to come off first.
To go with the theme of the rest of the bike the header bolts are mismatched and neither are correct.

Pipe is looking pretty rough in general. I do have a new cheap one on order from Asia. Might not see it for a while however.

Looks like the restrictor washer has been removed from this one already.

 

[JWC86]

Next I looked at taking off the bottom bracket that the foot rest and rear brake pedal mount to.

First thing I noticed was this odd looking bolt (SAE coarse thread) holding the rear brake on. There is suppose to be a stub shaft that must have got broken off and then the lever gets retained by a e-clip. Someone just "welded" a 1/2" SAE nut on. I'll give them credit that it works well but probably not how I would have went about repairing this.

The rest of the bracket is pretty rough. Bent in everyway and the hole for the kickstand is wallowed out bad. It would be repairable but for the $50 CAD for a new OEM version I'm just going to get a new one and be done with it.

 

[JWC86]

Tear down time:

Motor out

Rear wheel off

and all the rest:

I found this surprise on the frame:

Also it looks like someone has been here before:

So I will be starting with the frame repair, then most likely sandblasting and painting the frame.

 

[JWC86]

I have access to a shop with a mig welder and a sand blast cabinet so I took the frame, swingarm and a few other parts there.

First I repaired the frame. O forgot to bring my die grinder so I had to do everything with a angle grinder with a zip disc and a low grit flap wheel so this made prep and cleanup/blending somewhat tricky but it still turned out ok. Keep in mind I'm a self taught welder that only welds a couple times a year.

Here is the crack in the frame prepped:

Welded and blended:

I had cut the gusset off to have better access and it had been welded on with bubblegum welds by someone else. So now I welded that on with slightly better bubblegum welds.

Here is before:

After:

I debated leaving it like that but since they aren't the best looking welds I decided to blend it in. This is where the die grinder with a sanding wheel would have been nice.

I meant to take some close up pics after sand blasting but forgot. I did look somewhat better after sand blasted thou. I got good penetration on most of the welds so it should be strong and that's what matters anyways.

Here is the frame after sand blasting: