Yamaha HS1 90 twin top end build

[@jamesws3]

Wow, great spotting on the ring and pin issue. I'd have never noticed it. Never would have expected such an issue with a factory part. Its this attention to detail which sets your channel apart. Well done!

[@montana2strokeracer]

Thanks Jim, it was a fluke for sure. Never seen it myself, got a new piston in the post today, so should be able to get this little gal up and running soon.

[@RicardoValdes-r6w]

Good morning my dear friend and brother Dale, waking up early to watch your excellent show. I am always so grateful to the Lord and in that appreciation grateful to the Lord for you and for the great mind and spirit the Lord blessed you with..!! Sending you from Southwest Florida a big hug dear brother Dale..!!

[@montana2strokeracer]

Thanks Ricardo, got another on the way, so should be back on this project soon. Hope you're staying safe and clear of those storms down their brother.

[@RicardoValdes-r6w]

@@montana2strokeracer Thank you dear Dale, praying that my wife and I and all in Florida stay safe. I truly appreciate you..!!

[@RicardoValdes-r6w]

@@montana2strokeracer You are welcome dear Dale. I wish I was riding a 2 stroke along with you in another 2 stroke and feeling the cool air out in the high country..!! 😊

[@104ducati]

Good video, thanks. Had that pin problem a couple of times with aftermarket pistons - didn't notice initially, but on start up there was that unmistakable ringing noise, fortunately didn't break the ring, etc. So I drilled and repositioned the pin, half in the groove type, so a small section of old piston skirt fashioned to act as groove filler to prevent the drill bit wandering. First filed off the old half pin with a fine instrument file - 🙏- glad to say it worked!

[@montana2strokeracer]

Thank you, this is my first time in the bucket for this problem. Your solution is kind of what I was thinking also. But I was able to find a new piston, but I might try the fix later nothing to lose, would make a good video I think, whatever the outcome.

[@petermckee1061]

Hi Dale, finally got to see this all the way through. Been a crazy couple of days. Such a pain in the rear with that piston. Many would have passed that error over but it was your experience that put you right. That and your meticulous work. Looking forward to your resolution. Keep these excellent videos coming, mate. Cheers, Peter.

[@montana2strokeracer]

Thanks Peter, found a new piston, arrived in the post about 15 minutes ago.

[@RicardoValdes-r6w]

Thank you dear Dale for another great shop and work by you blessed brother. No worries for all will work for you to complete this bike’s project. God bless you brother Dale. !!

[@montana2strokeracer]

Thank you brother

[@ardtessa]

Hello again Dale ! My trick to put the washers on in hard to reach depths is to slide one on a philips head screwdriver, put it's tip on the stud and let go of the washer and it'll drop right in place. Cheers, Ard

[@montana2strokeracer]

Awesome Ard, good trick for sure.

[@retromechanicalengineer]

Hey Dale, your careful method of working and diligence has definitely paid off. That could have been nasty in less experienced hands. I agree with the chap that commented on the red dot, quite possibly a quality reject that found it's way into the aftermarket. Hopefully you get positive news on a new piston soon. Best wishes, Dean.

[@montana2strokeracer]

Thanks Dean got one on the way my friend. Yes, no argument from me. Think the red dot means "Dale bought a bad one" I have this stuck in my brain now, no more screwed up pistons.

[@steveh7823]

Hi Dale, good to hear a new piston is 'overnighting' to your shop. Kudos to you for staying calm during that frustrating episode, I would have blown gasket considering the high price and scarcity of parts.

[@montana2strokeracer]

Hey Steve, I have a replacement on the way, frustrated I was, and at time when I was younger.... yes a gasket would have been blown. Age has calmed me considerably.

[@oldgreybeard2507]

Catching up again. Thanks for posting Take care

[@montana2strokeracer]

Thanks for watching, sure appreciate it. Found a new piston for this one, will be full steam ahead on this project.

[@oldgreybeard2507]

@@montana2strokeracer just thinking. If I had that problem and I let the missus loose she would have ended up with two pistons. She is small but she has a sharp tongue!

[@vintubeable]

Hi Dale... Glad to be back at your shop and watching the Yamaha 90 twin, final leg of assembly. It was unfortunate, that the piston no. 2 turned faulty. I am not too sure, but theoretically the ring ends are spaced 180 degrees ( radially) apart for a two ring pison. More the rings, the angle reduces... like it can be 90 degrees for a 4 ring piston. This may be done to reduce the blowby as much as possible. But now, I guess each manufacturer have their own way of specifying the ring end postions, based on multiple factors. Anyway, hope you are able to get a replacement piston soon and continue the show.... Good Luck ! 👍

[@montana2strokeracer]

Got one on the way, should be here in a few days.

[@Free_Ranger_CT110]

Called into my local Yamaha dealer yesterday Dale & amongst all the new bikes they had an old YL1? 100cc twin. Such a great looking little bike, but man it's tiny! The twin exhausts looked so good & it was for sale at AUD$6k, approx USD$4100. Never seen that problem with a piston before, very frustrating.

[@montana2strokeracer]

Wow Darren, that's about what they go for here in good shape, I have a AT-90 which was the Japanese market only version of the YL1, it uses these same pistons. I put new rings in it that I bought for a HS1 twin like this one. I have some YL1 pistons on the self here and those have the pins in the intake side not the exhaust like this one. Weird I say. The only drawback of the YL1 is the 17-inch wheels and a 4-speed transmission. Thats why these 90's are so sought after is for the larger wheels and a 5 speed.

[@peteregger7928]

Good catch! I'm sure that ring gap would snag the port and then disaster would ensue!

[@montana2strokeracer]

No doubt Peter, if it hadn't been a twin, say it was a single cylinder, I have to wonder if I would have questioned it. Maybe luck prevailed.

[@richb419]

HI Dale, good catch, not sure if I would have noticed the problem with the piston. Rich

[@montana2strokeracer]

I don't think I would if this engine was a single cylinder but being a twin it was just weird that one was one way and the other a different way.

[@markjones95]

Thats bad luck on that piston Dale. I guess you could press the ring locating pin all the way in on the side that doesn't locate into a boss, but not sure if the drilling would be deep enough on the side that does go into a boss. Drilling the new holes looks a challenge too. Worth a try though if its scrap otherwise.

[@montana2strokeracer]

Yes Mark, a chore it would be, I did find a replacement so it's not a have to thing. But it might make a good video in the future, can't mess it up any more than it is.

[@k4106dt]

I didn't realize that the transfer ports curve around to the rear of the cylinder above the intake port like they do. This is probably done for better scavenging. That left an unbroken zone between the exhaust and transfers for the ring gaps. Hope you find a replacement piston soon.

[@montana2strokeracer]

It is an interesting design for sure, I have found a piston and it's on the way.

[@k4106dt]

@@montana2strokeracer As always Dale, looking forward to the next video.

[@frankdillon6127]

can the pistons be used on either side can they be switched right to left and left to right. would that put the pins in the correct position. so small i cant see the problem with my 80 year old eye balls.

[@retromechanicalengineer]

Unfortunately Frank, the pegs will still be to the rear with the arrow pointing forwards. Best wishes, Dean.

[@frankdillon6127]

@@retromechanicalengineer thanks Dean ,so unusual to get a bad piston as Dale mentioned. just a engineering hiccup i guess.

[@montana2strokeracer]

Hey Frank, Dean is right on, they just messed up on this one. Did find another though, it's on the way.

[@markaddy53]

not good dale bet you woz gutted hopefully new piston will be good great work as usuall next video please

[@montana2strokeracer]

Got another on the way Mark, lucked out.

[@frankdillon6127]

Me, here!

[@jamesbanjomanjohnson]

all i can say is WOW, sounds like something that would happen 2 me, if anybody can fix it dale it's you, just another challenge...

[@montana2strokeracer]

Thanks brother, I found a new one. But it would make a good video.

[@azlandpilotcar4450]

Nice work, and good that a new one was located post production. Was there a yamaha 50cc scooter of a similar bore size? Maybe a part number mixup at the warehouse?

[@montana2strokeracer]

Thanks Dave, there was a 50cc, but the piston was larger, and the stroke was shorter. They just messed up on this one, got another on the way.

[@RicardoValdes-r6w]

Certainly I would hope the supplier can provide you the replacement for another piston sets..

[@montana2strokeracer]

These parts are NOS (new old stock) they are no longer serviced by the dealer or the manufacture. You're on your own if you buy them.

[@RicardoValdes-r6w]

@@montana2strokeracer Limited resolution with parts..

[@johnb5519]

I was looking forward to hearing it start up, but I guess well have to wait. How to remove those pins. An EDM machine could do it, but if there isn't one around?

[@montana2strokeracer]

Well John the wait will be short, I located a new one and it's on the way. My thought was to use a Dremel and grind it down and out of the ringland. then just drill and relocate them.

[@johnb5519]

@@montana2strokeracer Yeah, if there's enough room, sounds good to me.

[@oodiddy9778]

Dale would it not be easier to bore it out to fit the oversize pistons if the anti rotation pins are correct on the oversized piston than messing about with the faulty piston pins?

[@montana2strokeracer]

The 2nd over set is earmarked for another set of cylinders that I have in the shop. I was able to find another piston, it arrived today, should be able to get this project moving forward again. May try to relocate those pins later though, might make for a good video......nothing to lose.

[@oodiddy9778]

@@montana2strokeracer it will make a exelent video.

[@MrBeagleblue]

Hey Dale you might want to check they haven`t stamped the exhaust arrow on the wrong side of the piston, put it in with the arrow facing the inlet see if the ring pins line up correctly then?

[@k4106dt]

The piston has an asymmetrical skirt.

[@MrBeagleblue]

@@k4106dt But anyhow if it was stamped wrong it would be going on the wrong way. So if it if the skirts are asymmetrical you should be able to tell if was stamped wrong.

[@montana2strokeracer]

If you remember in the video, I looked at all that. I considered the offset of the piston pin hole, locating the offset to the rear which should put the arrow to the front, it was.....but the ring pins were to the intake instead of the exhaust side. They just mess it up. Got another on the way, should be a week or so.

[@MrBeagleblue]

@@montana2strokeracer Cool.

[@JohnWilliamson-uc8md]

Maybe you might press fit the pins flush, or just below flush then you might be able to install some of the correct size where they need to be.

[@montana2strokeracer]

I actually thought I would just grind them flush and clean up the ring groove with a Dremel then just make new ones from brass rod and poke them in where they should be. I may do that at some point, but I was able to find a replacement, it's on the way.

[@johnreid2837]

I have never seen that problem before.

[@montana2strokeracer]

Think it's a first for me too John. Located another and the pins are in the correct place so on we go.

[@donbridgewater2988]

That is a major mess up by the guy drilling the holes in that piston. You might as well try and redo the pins, you can’t mess it up anymore than it is now.

[@montana2strokeracer]

Hey Don, I may try it at some point it will make a good video, but I did locate another one and it's on the way.

[@earleclemans4836]

Why not use the second over set?

[@montana2strokeracer]

Those are for another set of cylinders that are more worn and will require .020 to clean up. I was able to find another piston for this project.

[@RicardoValdes-r6w]

Dear Dale, many years ago I used to apply about 4 ounces of Marvel Mystery oil to the engine of my bikes with the fresh oil change and about the same about to a full tank of fuel, question how do you approve or disapprove of that as a couple of mechanics suggested such application, these were certified motorcycle mechanics back in the early 90’s in Miami Florida my hometown. God bless you brother Dale.

[@montana2strokeracer]

I have done it too. Not going to hurt anything, it actually works better on four stroke engines though, that way they get the benefit of the MM oil as upper engine (valves)lubrication. Just like with automobile engines.

[@sidecarbod1441]

Hey Dale you will never be able to pull the pins out but you can use a very thin grinding disk in a Dremel to grind the pin so that in all respects it is flush with the ring groove. As to fitting new pins, well that would be very tricky, also what sort of press fit would you go for? Years ago when I was running a highly tuned 350LC I had cause to relocate piston ring pins, it did not work out too well in the end! 😞 Good luck to you if you try this mod!

[@montana2strokeracer]

That is about what I was thinking, just grind them out of the ring land. I don't know how you would determine the interference fit, but I would assume .002 to .003 would be good with the addition of some Rockset to retain them, for the heat would be too high for Loctite. I probably will not do it; I was able to locate a new piston.

[@sidecarbod1441]

@@montana2strokeracer I'm sure you would do a great job if you did go down this route. I attempted this I would always be worried that the pin might work loose, it would then no doubt destroy the cylinder!

[@montana2strokeracer]

Yeah I would worry about it too, and your right, it would be catastrophic in epic portions.

[@budlistar5312]

That red dot probably means REJECT but it slipped thru anyway.

[@montana2strokeracer]

Roger that Bud, exactly what I was thinking.

[@cainbeeping8480]

Wow what size is that piston? That is tinny.

[@montana2strokeracer]

They are tiny indeed, 36.50mm is the standard size, that's less than 1 1/2 inches at 1.437 inches.

[@cainbeeping8480]

Here

[@mikeflohr4043]

Could boar one cylinder and use a new 2nd over piston and rings, if worse comes to worst 🤔 But if had to bet on what your going to do, it would be your going to move the pins.😃

[@montana2strokeracer]

Hey Mike, the 2nd over set is earmarked for another set of cylinders that I have in the shop. I was able to find another piston, it arrived today, should be able to get this project moving forward again. May try to relocate those pins later though, might make for a good video......nothing to lose.

[@mikeflohr4043]

@@montana2strokeracer great 👍 but no shortage of projects for videos though 😀😃😆

[@mrutherford8590]

I’m in Nc with no power. But if you give me the part number I’ll go look in my boxes of oem Yamaha pistons and I’ll see if I have one for you

[@montana2strokeracer]

I am so sorry to hear of the disaster out there. My prayers are with you folks out there. I have been able to locate a new piston and it's on the way. Thank you for your awesome offer.

[@cainbeeping8480]

That sucks about the piston.

[@montana2strokeracer]

Yep, got it handled though.

[@kevowski]

Those pistons are so small..

[@montana2strokeracer]

They sure are, 36.50mm 1.437 inches.

[@Corey-dy2cq]

Dale I hope you have a neighbor apprentice to carry your knowledge on when you retire. Much of what you do can;t translate in videos. Needs to be learned by feel.

[@montana2strokeracer]

Thanks for the kind words, Corey. No kids today just don't seem to be interested in old machines like I mess with. If a young man showed interest, I would sure be willing to mentor him. You are right of course, just like anything we do, you get better at it and learn more by doing. I really though I knew a lot about these machines, but I learn more every day. It's good for me, to keep my mind engaged. Lots of fun also.