My Murray Monterey Build

junglepig

Active Member
Joined
Oct 30, 2018
Messages
220
Likes
66
#1
I thought I'd try to share my experience with motorizing this Murray Monterey Cruiser that I found on Craigslist. I used to be an avid cyclist, but I suffered from a medical condition in 2010 which has no cure and makes it excruciatingly painful to walk or pedal a bike. I haven't ridden since then. For mobility, I often use an adult Razor kick-scooter. I can use my right leg to push, and my left leg is essentially motionless. This is much less painful than walking and allows me to get around when I have to go places like my daughters' softball or volleyball games. I hope that this project can bring the joy of cycling back into my life. I'm sharing a little of my backstory so you will understand some of my motivation and also that I have major financial constraints. (Despite this, I intend to survive this project and will make safety a priority.) It is my first motorized bicycle attempt. My physical limitations also mean I won't be able to spend all day in the garage doing assembly. I have to pace myself and can work only in short intervals. I received my kit a couple of days ago. It's a generic kit from an eBay seller in California.

My first step was to begin installation of the rear sprocket rag joint. My kit came with the 3-piece collar and a 9-hole 44 tooth sprocket.
I plan to retain use of the coaster brake, and add a front (and possibly rear) rim brake.

Kit Hardware is GARBAGE!!
One thing everyone seems to agree on about these kits is that the included mounting hardware is worthless. As I began torquing down the 9 bolts around the sprocket I quickly proved this again by stripping the threads on several bolts.

My kit came with M6 x 1.00 x 40mm bolts. As I removed the bolts, I noticed the "spring" washers had no spring after being compressed and remained flattened. All of it went into the garbage. I don't have a good hardware store nearby, so I went to Home Depot. While metric fasteners were available there, they were outrageously expensive. (Just the bolts were sold individually at like $0.70/each.) So I opted for 1/4" hardware.
Since the rag joint had already been compressed, I was able to easily use shorter 1 1/4" long, 1/4" bolts. I also used new flat washers, spring washers, and nylon lock nuts. (These bolts about 32mm long vs the 40mm bolts from the kit. This left about 6 threads extending past the nut, vs about 14 for a neater installation.)
Without having any experience with this rag joint, I used my best guess about how tightly I should torque the sprocket. I just kept it as even as possible and adjusted any run-out by tightening an additional 1/4 turn or so on the bolts near the "high" side.

Coaster Brake
This bike has a Bendix coaster brake. My sprocket is dished or offset. I installed it per the instructions with the teeth closer to the wheel. My sprocket center hole was large enough to not interfere with the coaster brake cover. However, I did find it necessary to re-shape the coaster brake arm to clear the heads of the sprocket bolts. This was easily done by placing the arm in a vice and tapping on it convincingly with my favorite 3-lb hammer, "mini-Thor." Two main bends are required: 1 just beyond the square drive opening to let the arm clear the bolt heads. Then another near the anchor strap position to realign the arm with the chain stay. I'll take a photo of this and post it in the next day or so if I get to work on the bike.
I reversed the anchor screw so that the threads extend to the outside of the bike because I thought there might be interference with the drive chain.

Conclusion:
I think the result so far is satisfactory. I was able to achieve a reasonably true installation I believe (though if I had the money I'd probably use the 1.5" hub adapter and replacement sprocket.) I question whether I'll have adequate clearance between the tire and drive chain, and between the chain and coaster brake hardware, but I'm sure these issues can be addressed if/when they arise. I can reverse the sprocket if necessary, but I think in my case the "concave-in" arrangement will work best. We'll see!

Murray Monterey.jpg
 


bakaneko

Well-Known Member
Joined
Nov 16, 2015
Messages
1,122
Likes
217
#2
You will enjoy the build. Two things: I know some people say Lowes, Menards, Home Depot have metric nuts and bolts per unit but I did not find the selection or prices even reasonable. It isn't much the price, which you will pay more regardless because its metric, but rather the quantity. I need two bolts for the muffler and the store only offered packets of 20... Instead, I go to an Ace Hardware. They have a good selection of different metric nuts and bolts and have them per unit. Still expensive, depending on bolt grade and head style, but atleast there is a good selection and its per unit.

Also, depending on the extent of your injuries, you might consider putting on a 500W+ electric front hub kit. Rear is better for traction but its hard to do with a gas motor kit. On most of these two stroke kits you do need to pedal to 5-7 miles before releasing the clutch and its even better to pedal to 12+ after to reduce stress on the engine as you throttle up to speed. With a 500W kit, this will help you get going only and then use the gas engine. You won't need a super large battery since its just for getting underway and perhaps big hills.
 
Joined
Jul 2, 2018
Messages
207
Likes
99
#3
I hope that this project can bring the joy of cycling back into my life.
No worries there. The first time you ride it you'll be giggling like a schoolgirl.

A couple of safety tips for ya (I understand you're on a budget so I won't go into the REPLACE ALL THAT GARBAGE WITH HIGH_BUCK STUFF tips):
1: If you're going to use the wheels and brake that came with the bike, take the hubs apart and put some good grease in there. Most of the time the grease that comes with the bike is just about good enough to hold the balls in, but near worthless for lubrication at motorbike speeds. It's cheap insurance.
2: Blue Loctite is your friend. These things vibrate like crazy. Again, cheap insurance,
3: Limit yourself to short rides at first. Something's going to break or reveal a weakness, and it's nice to be close to home when it does. I've found that if you can make it 10 miles without a breakdown or urgent repair, you're good to go just about anywhere.

What kit did you get? We can point out weaknesses and workarounds with a bit more info.
 

junglepig

Active Member
Joined
Oct 30, 2018
Messages
220
Likes
66
#4
Thanks for that. I did inspect and grease all 3 bearings in the rear hub when I put the sprocket on. I will get some Loctite today. I jam-nutted the motor mounts and exhaust manifold, which I finished up yesterday. I had to get a little creative with the motor mounts. I'll post photos of what I did later rather than describe it in detail.
I pulled the head before I installed the engine, and inspected and pre-lubed it. Is this normal for the cylinder liner wall to be in such crappy condition out of the box, or did I get a sub-par piece? Also, as I reassembled it, as I approached 9 ft-lbs on one head bolt it felt to me like the threads were about to strip, so I torqued all four to 9 ft-lbs and left it. When I find some 8mm all thread I'll replace these. According to the kit instructions the spec is 12 ft-lbs.
(Oh, and the kit was from an eBay seller. It was described as an "Updated" 80cc kit. It is the "silver" version with chromed muffler. It said it had a 47mm x 40mm bore x stroke, but I did not measure either while I had it open. It was packaged well and nothing was damaged or missing.)

I really appreciate all the help and tips!

I have everything on but the clutch lever/cable and chain/tensioner. It is possible I'll start the engine and get a first ride today.
View media item 61566
 

junglepig

Active Member
Joined
Oct 30, 2018
Messages
220
Likes
66
#5
So, I got out this morning and finished my first build. Then I watched the Falcons beat the Redskins with my fiancee'. Then I went to the store and got a gas can and 8 oz of two-stroke oil and 1 gallon of what passes for gasoline here. Went home and fired my new bike up for the first time. Yay!

So, here are a few more comments about the build, and then about my first few rides, and where I'm going from here:

TLDR: Two thumbs up, way way up!

Tank:
Nothing special here, except that I did not have either Loctite or extra nuts when I installed the tank to the frame. After my first rides, the tank managed to loosen itself. I have since applied blue Loctite.

Clutch:
My handlebars are standard 7/8", but the hand grip area is just a little larger. I tried to open up the spacing on the new clutch lever, but that "metal" is very brittle, and I broke it. The good news it that it didn't really matter. I put it on anyway, and it clamps down on the bar just fine. I'll replace it before long.
IMG_20181104_142913789.jpg
I repositioned the clutch control arm so that the cable pull is more in a straight line. I don't know why they put it the way they do from the factory. Moving it does mean the cable set screw is now under the carburetor and thus harder to get to, but it only take loosening one screw to move the carb out of the way anyway. But the cable force vector is now perpendicular to the arm, so operating the clutch lever is easier on me and on the cable.
I also discovered that the free end of the clutch cable tucks conveniently into on of the air cleaner holes. :)
IMG_20181104_142836752.jpg

Chain:
The chain installation was straightforward. I had to remove one link. I used my grinder to bring the pin flush on both sides of the link, and then used a punch and hammer to tap the pin out and remove the extra link. I put the chain on, and then went to work on the tensioner.
First, I removed and discarded the crappy washers that it came with, and used new 8mm flat and lock washers, and nuts.
I applied some lithium grease to the bolt and bearing (though that bearing is sealed) and placed the assembly such that the chain was tight enough with all the adjustment taken out of the tensioner. I used the new hardware to clamp it in place, and then used the original nuts as jam nuts. I don't want the tensioner moving!

After installing the tensioner, I pedaled the bike around the yard with the clutch disengaged just to make sure the chain and tensioner operated correctly. They did. Satisfied with that, I installed the chain guard. I had to take a corner off the rear with my grinder. I installed the front with a 6mm nylon locknut, and just used a black zip-tie for the rear.

Spark Plug:
I gapped the plug to .028" based on a quick Google search, although I just noticed my booklet specs 0.6-0.7mm, so .025" would've been perhaps more correct. No worries though. I will note that the plug definitely needed to be gapped. It was ridiculously wide as shipped in the kit. (Like, maybe .060" or so.) I also applied a little aluminum anti-seize to the threads, installed it finger tight, and then gave it about 1/8th of a turn past finger tight.

That's about it for my build. Other than the crappy hardware, everything went together well. I went and watched the ball game and rested, then went to the store and got my fuel.

First Ride:
Wow! What a bunch of fun! She started right up, and after a minute or two I took off the choke and adjusted the idle speed. It was dark already, so I was wearing both a lithium headlight and a helmet. I rechecked everything and gingerly took her around the yard a couple of times, then rechecked that the chain and tensioner were secure, and that there were no major leaks. I later discovered a slight leak from the plastic in-line fuel filter. Not from the lines or the barbed fittings, but from the seam where the two pieces of the plastic filter join together. I'll replace this tomorrow, and install some real fuel line too.
After I had some confidence that the rag joint and chain and sprocket and tensioner were all stable and secure, I took it down the road. (I live on a mostly untraveled country road, so no worries about cars.) It's about 1/4 mile to a little church, where I turned around and returned home and checked everything again. All good except I noted the slight fuel leak from the filter at this point. I did this trip twice more and then decided to chance the rather long and steep hill the other direction from my house. I wasn't sure if the little 70cc motor would be able to pull my 175 lbs up the hill without straining, but it did. When I returned from this trip, I noticed the fuel tank nuts had loosened from vibration, so I applied some blue Loctite to the threads and retightened them.

Conclusion:
I'm totally jazzed, stoked, whatever! I really did not know exactly what to expect going in.
All my uncertainty/anxiety about the chain/tensioner/rag joint/coaster brake/motor mounts is now relieved. I was able to get everything to fit without interference issues, and it seems sturdy and true.
I do keep reaching for the currently non-existent front brake lever! I hope my front brake kit comes soon.
This bike is meant to be some fun for me. Something I can tinker with and enjoy. And to allow me to get out on two-wheels again without spending a lot of money. So far it looks very very promising.

To Do:
Front brakes!
Speedometer.
Horn.
Head and tail lights.
Fenders?
Electrical system. (I plan to run a 12V system from the white magneto wire. I plan to rectify the AC, then boost it to 12V and use that to charge either a 4s set of li-ion cells or a bank of super-caps.) I can use this to run some nice bright LED lights, horn, and maybe charge my phone.
I have everything I'd need for the electrical in my component horde already. I'm going to keep my eyes open for a parts bike that has good chrome fenders on Craigslist/Facebook. I've ordered some of the other stuff. It's coming on the slow boat though. So I'll add it as it comes in.

Thanks for the help everyone. Sorry for the long post. I look forward to sharing what I do, and seeing what others build too.
 
Joined
Jul 2, 2018
Messages
207
Likes
99
#6
Be careful with the fuel tank. There's about 1/8 of a turn between "still too loose" and "crap, I pulled the studs out." Glue some rubber to the top tube of the bike under the tank (an old inner tube works for this) to give the tank some traction on the tube.

Welcome to the madness.
 
Joined
Jul 2, 2018
Messages
207
Likes
99
#7
That cylinder wall looks nasty, but it'll probably coke up some as you run it, filling in the imperfections. The rust is near enough to the bottom that it shouldn't affect compression. I'd run it, but wouldn't be happy about it.

Good enough is the enemy of perfection, and vise versa.
 

junglepig

Active Member
Joined
Oct 30, 2018
Messages
220
Likes
66
#8
Fortunately, there's no rust. That's just a reflection. Probably some overhead fall foliage. I'm not certain what the right metallurgical description would be for the dark spots. It's smooth enough to the touch, not pitted. I'll be curious to see how it fares long term.
 

junglepig

Active Member
Joined
Oct 30, 2018
Messages
220
Likes
66
#9
Here's a new photo with the speedometer and chain guard installed, and the seat lowered to make mounting easy :sneaky: and to make it look a little more "vintage.":cool:

View media item 61578
I'm up to about 15 miles on it.

One issue today is that she suddenly quit pulling. The crank gear came loose and spun off. I shut it down and pedaled the short distance home. I could find no evidence that there was ever a Woodruff key installed! I have some ordered for it, but for now I just reinstalled and tightened the bolt as much as I could. I believe that's how it's been. I believe I must've kicked it loose by coasting down a hill and then popping the clutch near the bottom. I'm guessing that may have tended to unscrew the bolt in the end of the crank. Probably stresses the chain tensioner too. Maybe I should avoid doing this(?)

I received and installed the mechanical speedometer today. It's the common "Sunlite" brand marked in mph with the crossed checkered flags on the dial. I haven't checked to see how accurate it is, but it seems about right. While I had the front wheel off, I cleaned and re-packed the bearings. I also lubed the speedometer cable with a little lithium grease.

Very much enjoying the bike and the new hobby.
 
Joined
Jul 2, 2018
Messages
207
Likes
99
#10
That speedo is fairly accurate. Its accuracy is dependent on tire size. If you're running a 26x2.125 tire it's going to read a trifle slow, like half an mph at 20 mph. If you want an accurate read, do a run with GPS (or phone app) and compare. Then you'll know that 25mph indicated is 23mph actual, or whatever, and you compensate mentally.
 
Top