Topic: Honda S65 Project

[hoodellyhoo]

I’ve been slowly (ok, very slowly) working on this S65 since 2015. It’s in rough shape with plenty of corrosion, but the good news is that it’s complete and nothing is seized up or beyond fixing. Where most would see this as a parts bike, I see a machine begging to be brought back to life.

My goal for this bike has been to get it back on the road by spending as little money as possible. Where possible, I’m making the original parts functional while the cosmetics are generally a low priority. A good example is the wiring harness. The original was chewed up by mice in several places. While NOS harnesses are available, I went the route of buying a cheap used CM91 harness and splicing portions of that into the S65 harness so I’m left with something that retains the original wire connectors and wire colors.

Someday I’ll make this a proper project thread so I can show pictures of the work that’s already been done, but what I’m currently pondering is the exhaust system, specifically the muffler. The original unit is so rusted it’s officially beyond saving (though I did consider for a time trying to patch it up with some sheet metal and copious amounts of hi-temp sealant). While a very attractive repo unit is available from Thailand for $155 shipped, that’s out of the budget right now and I’m afraid all that new chrome would force me to tear down the rest of the bike for a full restoration just to make it match.
 
Cheap and easy muffler solutions abound but what I absolutely don’t want to do is annoy my neighbors with a loud BRAAAAAAP every time I take this thing out. What I want is a muffler that is every bit as quiet as the original (*with the exhaust diffuser in place). From what I can tell, most of the cheap universal mufflers sold are generally just a straight through glasspack style which won’t give me the quiet purr I’m looking for. The diagram below shows just how much went into making the original muffler so quiet.


The two options I’ve considered most are this:

1)   Convert to a repo (or good used) system from a C90/S90 or Cub. These are cheaper than the repo S65 system and from what I can tell, would bolt right up to the S65 frame and engine. I think the only modification necessary would be to switch to a Cub or S90 rear brake pedal. These pedals are designed to go under the exhaust pipe whereas the S65 pedal would interfere with the low exhaust. The biggest drawback to this choice is cost, as well as losing the original look of the high pipe system.

2)   Which brings me to option #2 and the current frontrunner. These aftermarket small engine sausage-type mufflers can be had for $5-$10 a piece. They consist of a central perforated tube running through the outer shell, with a baffle plate in the center. My thought is to weld 3-4 of these together and I’m hoping that will get me the quiet muffler I’m looking for. I think I’d even like to hide this inside the rusted remains of the original muffler just so I can keep the original look.

What says the SOHC4 brain trust? Is there another cheap option I’m overlooking? Do you think option #2 will work?

[Stev-o]

Hey Hoo....looks like a fun project.  I vote for #1, buying a used S90 exhaust and modding it to fit.

Not this one, but along these lines...

https://www.ebay.com/itm/64-Honda-Dream-Benly-150-CA95-Right-Exhaust-Header-Muffler/254331642648?fits=Year%3A1965%7CMake%3AHonda&hash=item3b3758e318:g:bBEAAOSwERhdVbtZ

Someone here prolly has an old muffler laying in the garage, post up in the wanted section.

[scottly]

My thought is to weld 3-4 of these together and I’m hoping that will get me the quiet muffler I’m looking for. I think I’d even like to hide this inside the rusted remains of the original muffler just so I can keep the original look.

Just how bad is the original muffler? If it's good enough that it could hide a few Briggs and Stratton mufflers, maybe it's salvageable?

[hoodellyhoo]

Just how bad is the original muffler? If it's good enough that it could hide a few Briggs and Stratton mufflers, maybe it's salvageable?

Several large holes, and it's full of mouse nest. If the internal baffling was in better shape I would consider it, but even that is rusted out too.

[Johnie]

Trevor good to see you back at the bikes! I think I mentioned the S65 was my first bike. It was the white model. Good luck with it.

[hoodellyhoo]

Well... for anyone that cares I'll give a crash update on what's been slowly happening with this project of the last few years. Spoiler Alert: Not quite road ready but getting closer!

To address the question that first started this thread, I made the decision to make the bike look like an C200/S90 with a replica low exhaust for a C70. I spent a good long while researching part numbers and examining pictures to try and figure out how to make it work. While not a direct bolt-on, it hasn't been too bad and I'm happy with the look. See pictures below.

Spring 2020 to Spring 2022:

Moved the bike to the basement to make working on it easier.

Removed the wheels an installed new tubes/tires (with help). The whole bike is covered in thick surface rust so I was glad to see the inside of the rims looked absolutely pristine. I think this bike just sat in a damp garage for years and years.

While looking at pattern exhaust parts on ebay I found a set of footpegs for a trail 90 that incorporated a side stand (which the S65 never had). Since the original footpegs were pretty bent, and I thought a side stand would look neat, I bought a set.

Took the motor out to begin disassembly. Ever since I've owned the bike I knew it needed top end work as it was loosely assembled and had a blown head gasket.

[hoodellyhoo]

Spring 2022 Continued:

This bike never head a title, so I decided to try the Wisconsin bonded title process. It wasn't too bad at all but took a few months and I think all-in cost between $300-500 (I can't recall) for the title and WI collector plate.

April I got a package from Thailand with a bunch of replica parts:
*C70 exhaust
*C70 exhaust bracket
*OEM style mirrors
*C70 brake pedal (Since the original S65 one is straight and wouldn't loop under the exhaust like an S90/C70/etc)

Spring/Summer 2022- Continued to disassemble, clean and inspect the engine. Disassembly revealed heavy scoring on the top of the piston. I made the (wrong) decision to install another standard size piston & rings. Lapped the valves, honed the cylinder, etc. One of the valve covers required heat to loosen.

The pattern C70 brake pedal had two problems: 1) The pivot hole was much larger than the original. Not much I could do there but maybe I'll try and make a shim someday. 2) The arm the rod attaches to was much taller than original and would hit the engine cases and brake light switch, so I shortened it with a grinder and made a new hole for the rod.

[hoodellyhoo]

July 2022-

The wiring harness was all chewed up by mice. Too cheap to buy a NOS or used one off ebay, I had started repairing it in 2016 with parts from a CM91 harness I snagged for cheap off ebay. Fast forward 6 years and I finally completed the job.

I also started reassembling the motor. The gaskets must have been thinner than OEM because when it came time to install the cylinder castle nuts, they bottomed out before tightening the cylinder. Parts stash to the rescue! I found enough 10mm nuts to get the job done (I remember two came the top mounting plate of a spare CB750 airbox I have)

[hoodellyhoo]

August 2022-

When I got this bike it was partially disassembled. Think lots of nuts & bolts in coffee cans and baby food jars with labels. The time came for me to reinstall the cables and unfortunately there's no diagram in the service manual to show proper routing. A lot of google searching turned up no good pictures of an S65 with the tank removed. On a whim I went digging through the box that the extra parts had come in and low and behold, there was a handmade diagram from the previous owner to show the cable routing!

With that out of the way I continued with reinstalling the carburetor and oil lines, and reassembling and greasing the throttle assembly.

[hoodellyhoo]

August 2022 Continued - Final Assembly!

Next up was making the C70 exhaust fit. In a nutshell, this meant enlarging the mounting bracket hole to lower the whole exhaust so that it was straight and cleared the engine. Then I had to bash the heck out of the bracket to move the muffler closer to the inside so that the kick starter would clear and the muffler wouldn't jut out at a goofy angle. I also ended up needing to buy some thicker exhaust gaskets in order to seal up the head pipe connection.

With the muffler 90% in the right spot I used furniture moving straps to bring the bike back upstairs and continue assembling in the living room.

Another aesthetic choice I made was to replace the original side covers with a repo set for a C200, mainly to eliminate the original right side cover which is notched to clear the original high pipe exhaust. It was then that I learned there's enough difference in width between the S65 and C200 air filter that I would need to find a C200 filter. The S65 one is wider and pushes the C200 side cover away from the bike.

With the seat, tank, and side covers on it was time to wheel it outside into the sunshine and enjoy the fruits of my labors. Yes, I'd still like to get rid of more of the rust, but overall I'm really pleased with how my low-pipe S65 turned out.

[hoodellyhoo]

Next up was trying to start it for the first time. Wi the the valves adjusted and spark confirmed, I kicked and kicked and got a whole lot of nothing. Inspection revealed the float wasn't dropping to let fuel in the bowl. I forget what I did to fix that, but then the issue was a heavily leaking bowl gasket. Luckily that cured itself after a while as the fuel swelled the gasket enough to seal.

With that out of the way, a few kicks brought it back to life with just a little smoke from the assembly oil.

https://www.youtube.com/shorts/CrmlJVgEYTU

It was running great! The throttle and clutch had a lot of slop in them but I was able to take it up the road and confirm that my transmission wasn't afflicted with the infamous "S65 popping out of 2nd gear". All was right in the world until.......

[hoodellyhoo]

I went for a longer test ride later that evening. After a few miles of successful riding I was about a mile from home at 35mph when the engine suddenly lost power and the lights dimmed. Immediately suspecting a piston seizure, I pulled the clutch in and coasted as far as it would go. Pulled off to the side I gave the kicker a prod and got normal resistance, so the issue wasn't a seizure. I pushed the bike a ways to get to a business parking lot that had some lights on so I could see what I was doing. I dropped the carb bowl and confirmed I still had fuel, so the issue must've been a lack of spark. With little more than a screwdriver and some pliers, there wasn't much fixing I could do. After trying to kick it a few more times and getting more nothing, I pushed it all the way home. Thank god it's such a little bike!

Despite being stone dead, it did look good there in the light of that parking lot..

[hoodellyhoo]

The next day I went in the garage, gave the bike a kick, and it started right up! WTH!?!? While this magical self-healing was nice I knew the problem wasn't truly solved.

After much investigation I figured the problem was likely the ignition capacitor that lives under the flywheel. Inspection showed what appeared to be some of the insulation to be failing and oozing out of the top as brown goop. Finding a proper replacement turned into a big headache. While Honda has made millions of these OHC horizontal single cylinder engines with a magneto ignition, this was one of the first iterations and even the S65 had something like 5 different part numbers for the capacitor and ignition plate. While there are many many cheap aftermarket capacitors available for these motors (mainly the CT70) , none of them matched the OEM one I had, ie they had different mounting plates or the holder for the points cam brush was in the wrong orientation. Hours of research eventually let me to an ebay auction for a NOS unit that matched mine. Money was sent and....a week later I got a capacitor that had the same number tag as the one in the auction but it looked nothing like the one in the picture. To add insult, after almost 20 years of ebay purchases this was the first time I encountered a truly worthless seller. Despite numerous claims, messages, and pictures sent they eventually ghosted me and never issued a refund. In the end it wasn't worth pursing further for a measly $15 or whatever it cost. After attempting to modify a capacitor from a CB750 points plate I gave in and ordered another NOS capacitor from ebay and got that one soldered in place. (side note, I think I've since found a new OEM replacement for this capacitor on the DrATV site if anyone needs one...) Another few kicks and she was back up and running as sweet as ever:

[hoodellyhoo]

Another test ride proved that....it still wasn't fixed. While accelerating after a turn the bike lost power again (this time more slowly) and died the same as before. The difference this time though is that after waiting a while I was able to restart the bike and gently limp it home. No pushing!

Not wanting to start randomly replacing parts, but with few potential culprits remaining, I ordered a replacement ignition coil and installed that. Just like before the engine started right up, except this time I had a "new" problem. Over the course of my testing I had suspected that the engine was getting noisier the more I ran it. Unfortunately after replacing the coil it was plain as day and it didn't sound good. This wasn't the gentle tick-tick of a loose tappet, the noise was louder and lower pitched. Getting my ear closer to the engine had me suspecting I was hearing a failed main bearing  It's hard to pick out in cell phone video, but the noise is there in the previous video. Without wanting to blow the thing up, I stopped riding it and basically left it alone for almost a year.

[hoodellyhoo]

Fast forward to July of this year-

I finally had the time and the desire to have another go at the 65. My goal was to get it back together for a local car show that was coming up in August (spoiler alert: didn't happen).

Taking the top end apart revealed some "good" and bad news. The good news was my main bearing wasn't the issue (so I didn't have to worry about splitting the cases and making this project last even longer). The bad news was 1) the top of one of the cylinder studs snapped off when I tried to loosen the nut on it and 2) My brand new piston was all scuffed up on the top just as bad as the one it had replaced  . So ever-worsening piston slap is the noise I was hearing. The question now was why?

In fairness, I hadn't measured anything when I reassembled the engine to check for clearances. Yes there was a little movement of the piston inside the cylinder, but I didn't think it was excessive and these engines have a reputation for durability in adverse conditions. In order to prevent ruining another NOS piston, I bought some micrometers and bore gauges to see what I had. The shop manual stated a maximum of .004" piston clearance and I was measuring about .0045". Now I have a hard time believing that excess .0005" is enough to cause that piston slap all on its own, but obviously I wasn't going to get away with honing out the cylinder and fitting another standard size piston. So what was causing this?? The truth is I don't really know yet. One commenter in a Facebook group said to check the centrifugal oil filter for blockage. This can starve the crank for oil, and supposedly the top of the piston is lubricated via oil being flung off of the side of the main bearing? So off came the right case cover and I opened up the centrifugal filter to find almost no debris. There was very little in the oil pump screen as well, so this investigation remains open. I'll check the oil passageways for blockage but given that there didn't seem to be a lack of oil all the way up at the cam, I doubt my piston slap issue was caused by lack of oil flow.


 

[hoodellyhoo]

So I turned my attention to the piston & cylinder where I had a few options:

1) Buy NOS or at least OEM style replacement piston and cylinder
2) Buy one of the numerous dirt cheap replacement top end kits from China. These cost about $30 shipped for a piston, cylinder, rings, and gaskets. A few bucks more gets you a complete cylinder head.
3) Bore the original cylinder for a NOS oversize piston & rings (which are cheaper and more plentiful than standard ones on ebay)

After striking out at finding a local machine shop able to bore a 63mm cylinder, I fired up the credit card and did both options 1 and 2. I did both for a few reasons. Mainly, even though the cheap kits all proclaim to be compatible with the S65, there are visible differences in the piston design. OEM pistons are tall with a high dome, while the cheap kits have a very short skit and a nearly flat top. I haven't confirmed it yet, but I think the cylinders are shorter as well. Since I couldn't find any evidence online of someone actually using one of these 70cc kits on an S65, I figured for 30 bucks what the hell. At the same time, since I was leery of how compatible the cheap kit would be, I searched for a more OEM style replacement. The closest I got was a 70cc C70 piston and cylinder from DrATV. This was nowhere near $30 cheap (more like $100), but the only NOS S65 cylinders I found were listed for $500 so $130 later I had two different top end kits.

Long story short, neither of the replacement piston & cylinders would work. Mainly, because the lower cylinder on both is too large to fit in the opening of the S65 cases. Sure, I could enlarge the cases but now you're talking about splitting the cases and I didn't want to go deeper than I had to. Also, both piston/cylinder combos were measuring at .004" clearance so I was afraid of repeating the same damage as before.

The other problem was the cylinders. The S65 and the C110 both employed a carb heating system that took hot oil through external pipes from the oil pump, up to the carburetor, and back down to the cylinder where it deposited the oil into the supply feed to the cylinder head. In the end this system was obviously deemed unnecessary as all subsequent models and all of the aftermarket cylinders lack the threaded bungs necessary for this oil system. While it is possible to add this connection to the later style cylinders, I didn't have the necessary machining tools to do it properly. Many owners bypass this carb heat system though as far as I could tell they all do it by installing a very short pipe straight from the oil supply to the cylinder. I could find no instance of someone simply blocking off all of the ports. I didn't want to try this either as this this carb heat system obviously supplies pressurized oil to the cylinder head, and even though I have yet to take a fluid dynamics class I'm pretty sure removing this feed entirely would reduce the flow of oil to the cylinder head. And that's probably not advisable.   

[hoodellyhoo]

So now I was back to option number 3, re-using my OEM cylinder so that I could retain the original carb heat system and not risk starving the cylinder head of oil. Then the question became how to get my cylinder bored oversize? The shop manual requires a minimum piston clearance of .0015" and a max of .004". Measuring my replacement +.25mm NOS piston, I knew I needed to bore the cylinder approximately .010" to get the necessary clearance. Taking a bit of a risk, I plunked down $80 on ebay and bought India's finest "sun style honing tool". The proper version of this tool was $400 but I figure at $80 for the knockoff I'd probably get more accurate results than if I had tried enlarging the cylinder with a simple ball hone or one of the spring-loaded master cylinder type hones.

Link to the tool I bought:  https://www.ebay.com/itm/225225833754?var=524167054329

Last weekend I finally had a go at it, and I think this will work just fine. I fitted the coarsest stones to the tool and went to work removing material and periodically stopping to clean and take measurements. The stones aren't as long as the cylinder, so an in/out motion is needed while operating the tool to try and keep things as uniform as possible. Using this method, I found I was able to slowly creep up on the proper dimensions. Once I was able to get the whole piston in the cylinder, a little further work on one end of the cylinder got me to a nice clean sliding fit the whole length of the cylinder. Periodic measurements show the bore to be reasonably uniform. Maybe .0005"-.0008" variation. Hard to tell with my economically priced measuring tools. I finished it off with a 320 grit master cylinder hone to knock down the high edges and give a nice cross hatch. Yes it's very much a farmer type fix and any proper machinist is probably wincing while reading this, but I'm feeling confident this will work.

The last update I have is the broken cylinder stud. I could buy a NOS one for $30 bucks, a used one on ebay for $18, or an aftermarket set of 4 with castle nuts for $14 that's advertised as compatible with the S65. I bought the aftermarket set and...shocker...they weren't compatible. Not only were they longer that stock but the top threads were M8 instead of the original M6. not wanting to give up, I whipped out the cheap tap and die set I bought when I first got into bikes and soon discovered that my M6 die had retired from the thread-making business. Facebook marketplace got me a genuine US army surplus tap and die set for $20 which did a great job of turning those M8 threads down to M6. A little hacksawing on the end and I had myself a perfectly functional replacement cylinder stud.

[MauiK3]

Looking forward to seeing the completion!

[Johnie]

Hey Trevor...nice to see you back at that 65! Good right up and I know you will get it solved and running. Keep us informed.

[bek1966]

Fantastic project Trevor.  I think the little Hondas make for the biggest grins, and I love the Honda S65's & S90's.  Thanks for the updates, I'm rooting for you!

Johnie, there is a very nice original white 1966 S65 on Facebook Marketplace right now.  It's just up the way in DePere.  Go get it before I weaken and succumb! 

Regards,
Brad

[hoodellyhoo]

Fantastic project Trevor.  I think the little Hondas make for the biggest grins, and I love the Honda S65's & S90's.  Thanks for the updates, I'm rooting for you!

Johnie, there is a very nice original white 1966 S65 on Facebook Marketplace right now.  It's just up the way in DePere.  Go get it before I weaken and succumb! 

Regards,
Brad

Thanks Brad! And glad I'm not the only one that thinks Johnie needs to pick up that 65. I keep eyeballing that other black one too, since I have most of the parts that it's missing.

[Johnie]

Been there done that SS65 show already. Go get it Trevor...I got a trailer for you.