Yamaha HS1 90 twin, will it run

[@wayneknodel3347]

Thank you, I just got 50 years younger this morning! These little Yamaha twins were the bomb back then for teenagers like me. I especially liked the 125 versions, both the road and scrambler models!

[@montana2strokeracer]

Hey Wayne. thanks for the kind words my friend. I know what you mean. I do have a 1968 AS1C 125 Scrambler that will be coming in the shop at some point. I share your interest in them too.

[@steveh7823]

Hi Dale, looks like an interesting project - with those tiny 45cc cylinders. A lot if it looks like really great condition for its age, like the chrome rims, frame, exhausts. I'm guessing the crank will look burned blue/black due to oil pump failure. It's such a pity that bikes get parked outside, sunburnt, saturated and frozen. They really need to be in a garage even more so than a car.

[@montana2strokeracer]

You won't get an argument from me Steve, I have already done the Japanese market only AT-90 that I found. Couple years back I think, just like this one, but faster. It didn't have the long carb slides to limit fuel intake like this one.

[@shawnmrfixitlee6478]

in the condition it's in , Very worthy of repair .. Thanks Dale !

[@montana2strokeracer]

I agree, good candidate, but really didn't count on a crankshaft rebuild.

[@jamesws3]

Amazing, Dale. Truly amazing. Hard to believe crank bearings are bad, but as always your diagnostic skills are spot on. What a blast from the past.

[@montana2strokeracer]

This one is going to be exciting; I have to make some tools to bust the crank in two. So, stay tuned for that.

[@douglasmeeker360]

Dale... the smile and memories when you fired her up! It's been 50 years since I've had mine. A '71 HS1-B. You're right on with the horsepower, my title showed 4.9bhp, and that was max legal for a 15-year-old on a restricted license. I wish I knew about the shorter slides! I think this project will definitely be worth it.

[@montana2strokeracer]

Just love the sound of these little twins, yes under 5 hp with the restricted license. Don't know if they still do that or not. Yes, that is the hot setup for the 90 twins, grab a pair of twin jet 100 slides. I have already found a set and they are on the way.

[@gigicocreates]

Wow Dale. that's unfortunate, but you are the guy to bring it back. Here's hoping it turns out to be a simple fix, even though I'm looking forward to the teardown!😉

[@montana2strokeracer]

Hey Gigi, yes, it is but will certainly be a source of some good videos. Hoping there are folks out there like yourself, that can benefit from them. Best of luck with yours.

[@petermckee1061]

Thanks Dale, bit late to the party. Well whatever awaits you within I know you'll deal with it with your usual skill. Looking forward to seeing what you discover inside. Cheers, Peter

[@montana2strokeracer]

I think the discovery is going to be fun to see. Just hope I can find the parts needed.

[@Brian12227]

Great to see you again dale, this looks like a good little project this bike is going to get some of that much needed love it needs. your the man for the job I can't wait to see inside the engine with you and I'm keen to see the rebuild on the crankshaf. I hope you can still get the genuine parts for it . see you on the next one thanks Brian.

[@montana2strokeracer]

Hey Brian, this is going to be fun. I have not done a twin or triple crank in a very long time. I am in the process of making a tool to separate the two cranks from one another. Back in the day we had this tool in the bike shop, doubt they are available these days. I really think I have a rod set for it. Believe it is the same for the AS1 twin 125. It is a aftermarket set though. Should be fine. Its the Labyrinth seal that I am concerned about finding.

[@retromechanicalengineer]

It's a great project Dale, just about all there. There is definitely carnage lurking in the crankcases and I'd be surprised if you didn't have two cylinders to bore, if its been run dry. No problem for the Sweger Workshop! Best wishes, Dean.

[@montana2strokeracer]

Yes, I agree Dean, we will see on the cylinders, think I have a set laying around somewhere, condition unknown but were not run dry like this one. These will have to bored in the lathe if needed.

[@robturton3162]

Looking forward to the crank rebuild Dale!

[@montana2strokeracer]

I am looking forward to the discovery process, hope I up to the crank rebuild. Parts are not easy to find.

[@donbridgewater2988]

Good morning Dale. Checking in to see what you have going on this morning.

[@montana2strokeracer]

More things happening here.

[@sidecarbod1441]

Years ago I came up with a rule that I follow when purchasing second hand 2 strokes....always assume that the engine is F$XCKED, that way you won't go far wrong! 😞 Another general rule is that you can't learn much from the fact that an engine will run or not, an engine might not run just because it has a small electrical or fuelling issue, don't then assume that the engine is knackered. (Although my first rule would still apply!). Also don't assume that there can't be much wrong with an engine if it does run, the engine in the vid runs but its knackered! I bet it will end up being a crank and re-bore job before it's sorted. Dale's the man to do it!

[@SeanCramer]

It will be interesting to see you do the twin crank, love your channel

[@montana2strokeracer]

Thanks Sean, haven't done a twin or triple in over 45 years, I know I will have to make some tools to do this one. Stay tuned my friend.

[@davidleland8729]

Sounds like your to do list just got a little longer there Dale. I'm sure you will be able to resolve the issues with the motor in no time.

[@montana2strokeracer]

Only takes time and money David. I'm retired, I have the time.

[@josephdangelo1503]

Hi Dale, that is one beautiful little darling there. Unfortunately it's like you said and I believe the same thing that the main bearings are gone sounds awful crunchy, hopefully the crank is salvageable. I've been thinking about trying to find a few of these old Yamahas and Suzuki's and work on them and getting them roadworthy or trail worthy again. I still have a few projects that I need to finish before that happens but wish me luck. I will wish you the same!!! Anyway my friend you keep on keepin on, many blessings to you and yours.

[@montana2strokeracer]

Thanks for the blessings my friend. The same to you folks. I think this one will be rebuildable if I can find the parts. Glad to see someone else having interest in these old bikes. They are fun and for the most part the parts are still out there. Think you will find them enjoyable, best of luck on your search.

[@josephdangelo1503]

@@montana2strokeracer 🙏🤙

[@bigmurr725]

Hey Dale , If that HS 1 didn't have so many good chrome parts I would say another flat tracker but that old Girl will make a real fun bike for around town . I dont remember if that HS 1 has a Labyrinth seal . Thanks Dale !

[@montana2strokeracer]

I totally agree Murray, this crankshaft does have a Labyrinth seal, not sure what I am going to do if it is worn out. I don't see any out there.

[@oldguysoldbikes]

Nothing that you can't handle Dale. A little shopping, some paint and some machine work and you'll have a rare beauty.

[@montana2strokeracer]

Cool old bike Jack, will be lots of fun.

[@frankdillon6127]

good morning Dale, coffee in hand lets get to work! LOL

[@montana2strokeracer]

Ok then, let do it.

[@markaddy53]

great little bike that dale had a few rd125 dx twin cylinder bikes thay woz pretty fast just had to keep adjusting the points to keep them on song get it ripped apart and rebuilt next video please

[@montana2strokeracer]

Right on Mark, finicky old points anyway!

[@cainbeeping8480]

That is a cool bike I think it is worth it to fix it.

[@montana2strokeracer]

Thanks brother, I think so too.

[@jamesbanjomanjohnson]

i think you got bad trouble on that one dale, but if anybody can fix it it's you,, the bike i had when i was a teenager was a 305 ym1 1966 if my memory serves me just right, iv still got the cutting torch dad traded it for, oh well iv still got the memories, catch you on the next one...

[@montana2strokeracer]

Thanks James, glad you still have the torch, but wouldn't it be cool to have the YM1? They are still out there my friend. This is going to be another fun project.

[@dennisboyd1712]

Yamahas are Bullet Proof

[@montana2strokeracer]

Yes, your right Dennis, but they do like oil.

[@daveallen8824]

Back in the day, a buddy of mine had a brand new Twin Jet 100 - A Yamaha 2 stroke twin even with electric start. I'm sure this was a predecessor or a cousin.

[@montana2strokeracer]

Yes, you are right the 100 was the first twin imported, the 90 as I understand it was imported for some states that require 16-year-olds to have a bike with less than 5 hp. The 90 was detuned by longer slides in the carbs, most folks change them to 100 slides and behold 10 hp.

[@frankdillon6127]

that old girl needs Dr. Dale for sure!

[@Ypvs350r]

I got a 100twin at my dads ,been in the shed since I was a kid, really rough but going to get it out soon and try to do a will it run video :), I swear the 100 looks way smaller then this 90 you have here , the 100 bike I got has a single gauge in the headlight bucket

[@montana2strokeracer]

Hey Kevin, yes, the Twin Jet 100 was a popular bike, I have the AT90, that I did several videos on, it's the same as your Twin Jet except it is a 90cc sold on the Japanese market only, mine probably was imported by a military member in the late 60s. This HS1 is a newer version of it, for the U S market in 70/71.

[@frankdillon6127]

would the crank bearings being bad eventually cause the timing to be off.

[@sidecarbod1441]

If the crank has enough wobble then it can affect the opening of the points but this engine has bigger issues than that, a wobbly crank can also allow air to get sucked in past the crank seals. The cylinder that was misfiring is probably scored up or the piston has smeared over the rings.

[@montana2strokeracer]

Yes just like the CT3 Yamaha I did about a year ago. If you remember while it was running if I pushed down on the flywheel it killed the engine. Made the point gap to wide. Sidecarbod1441 is correct.

[@frankdillon6127]

@@montana2strokeracer as i thought, back i 1969 i blew out 2 cranks on my TS-250 running premix 30 to 1 my mechanic said i needed to shift more, but during the heat of battle on the track thinks can happen. the Suzuki just stopped running he said the piston timing was changed when the bearings went south. probably the most fun i ever had racing T.T. and flat track!

[@stevepacitti9206]

More Botchery to deal with Dale, but you'll get on top of it! How are you getting on with the F7?

[@montana2strokeracer]

The F7 is still in cold storage awaiting the weather to improve to bring it in. Just had snow again last night. I am slow but do get them done eventually. But if you have been following, I did get the engine and top end finished a couple weeks back.

[@stevepacitti9206]

@@montana2strokeracer watched and enjoyed.😁

[@rowlandcrew]

It looked like the plugs were sparking alternatively. Is the timing alternate or simulataneous? are there two cylinder bikes with alternate firing?

[@montana2strokeracer]

The crank is 180 apart and there are two sets of points and two coils. Some of the twin Honda's for example, have a wasted fire on one side because they fire them from one coil and one set of points.

[@frankdillon6127]

Dale can your boring machine handle a 45cc bore.?

[@montana2strokeracer]

They will have to be done on the lathe Frank, takes more time and I will have to build a JIG.

[@jerrybigrig9475]

😎👍😎 .

[@tomstulc9143]

Didn't know they made a 90 I had a friends that had two 100s c Screaming ittle machine back in the day when I was a kid

[@montana2strokeracer]

They were indeed screamers, lot of fun. Yes, the 90 was detuned for under 5 hp for the kids on a restricted license. Under 16 in my state.

[@vincentricher9038]

Hey Dale that's gotta be rare I never knew Yamaha did twins that small will be a great project to watch. Are those front forks straight as they look bent.Or is it just the camera angle

[@montana2strokeracer]

This is the smallest twin to come out of Japan, they also made the AT-90 for the Japanese market. I don't think the forks are bent, it's from the wide-angle lens on the camera. I will be checking them through and straightening if needed.

[@johnfry9010]

That little bike will have some issues I'm sure "But ", I know a guy in Montana that is going to make it like new , going to be some good videos here !

[@montana2strokeracer]

Thanks John, I agree this old bike will make some good videos for sure. Hope that Montana guy is up to the task.

[@customgaragemoto7590]

👌👍👍👍👍👍👍

[@peteetwell826]

It is really a shame what some people do to motorcycles. There are those that should step away from the tools and then there is Dale that can fix just about anything!

[@montana2strokeracer]

You sure won't get an argument from me. Thanks for the kind words Pete.

[@DaleWesley-d7i]

😁😁😁😁

[@cainbeeping8480]

Here

[@garyfyvie9490]

key switch gone because bike will start when cut or unplugged thats all I know

[@montana2strokeracer]

I am sure you are right Gary, glad I have a title for this one.

[@garyfyvie9490]

It's good to see your going to work your magic on a twin 2 stroke those 200 & 400cc twins have a wicked powerband.