2 Stroke Engine Durability

[Mike B]

You really have to accept that these motors are a crap shoot.

Here is my front mount.

Now my motor works fine, something that actually amazes me, but this why I will never buy another. There is no way that this should have ever left the factory. I am using spacers to mount, so the eigth inch out of round is not really a factor.

But this is just not acceptable. Many here have had motors that did not run new out of the box. Some here have motors with thousands of miles.

Are you feeling lucky?

 

[Wippenshox]

I'm just trying to be nice and imform you of the obvious, see these nuts have caps. You couldn't over-tighten them unless you were a gorilla on meth.

Buying a $60 tool you don't need-priceless.

Thank you for the photo. I have seen a lot of these on bicycles. I'm sorry if my english is not the best. I just started learning it 2 years ago and I'm doing the best I can. My (Babylon software) dictionaries and Google apparently don't know what is a cap (mechanically speaking) either, so I rely on members to answer these little things. Thank you again.

EDIT: my mistake, I found that my dictionaries and Google know what it is if I type "cap nut". That appears to be the official name of this little metal part.

One of the very first pieces of advice I read was to get rid of the cap screws and buy real hi-grade nuts. I bought the sick bike parts head stud kit, two sets to be exact. One in 6mm and one in M8 1.00 for 66 cc motors.

Yes, this is a very valid recommendation. I know an awsome shop which is totally dedicated to bolts, screws and related. I'm definitely going there to buy high grade ones.

$60? I said nothing about an S&K torque wrench. I bought my 1/4" beam type 25 years ago at a used tool shop for $7. They don't have to be exact, just have to read the same every time.

Even here, in Brazil, a place where you pay lots of times more for a product than in other countries, I found nice torque wrenches for R$ 24,00 (U$ 15,00), which I think is considerably cheap.

For a proper head gasket seal you don't just torque to the specified torque from the start, you go up in stages. I start the M8 nuts at 2.5 ft lbs and go up 2.5 lbs at a time until I reach 12.5 lbs. You also don't go in a circle around the head tightening the nuts. I use a "Z" pattern or you can also use a "X" pattern. Failure to do this can cause the gasket to leak. You will know it's leaking when black oily crud is coming out from under the head. Ignoring this will cause what is called "torching". The hot exhaust gasses will burn a groove or tunnel out of the cylinder, ruining the head or jug. The head can be saved by doing the glass & sandpaper routine. Torched cylinders are toast, you then need a new one.

After a motor has been run a bit you need to check the torques on the head. Do this when the motor is cold. Hot torques can vary wildly when rechecked cold.

Aw man, thank you so much for coming to my topic.
All the infos are being organized in little topics in a Word document I'm creating.

You see, you're really helping me to develop this

You really have to accept that these motors are a crap shoot.

Here is my front mount.

Now my motor works fine, something that actually amazes me, but this why I will never buy another. There is no way that this should have ever left the factory. I am using spacers to mount, so the eigth inch out of round is not really a factor.

But this is just not acceptable. Many here have had motors that did not run new out of the box. Some here have motors with thousands of miles.

Are you feeling lucky?

Okay. I'm starting to realize the low quality of these engines now. Then, what would you recommend? Taking advantage of the chinese kit parts and using them with Honda stationary engines? That could be a good idea for durability and low maintenance, couldn't it?

 

[Diver]

Keep reefing on them you will pull the threads right out of the block then you get to deal with that.

Well then, don't "reef" on it. Common sense, save that $7..

 

[Mike B]

If you want cheap, then I suggest you build one up from a kit and a used good bike.

When it breaks, at least you will know how to fix it.

If you want something that really will go over 20,000 miles, then get a scooter or a small motorcycle.

 

[Wippenshox]

If you want cheap, then I suggest you build one up from a kit and a used good bike.

When it breaks, at least you will know how to fix it.

If you want something that really will go over 20,000 miles, then get a scooter or a small motorcycle.

You see, that's a problem. My family won't allow me to use a motorcycle or scooter. My two options are: car and motorized bicycle
I could consider bus, but I hate it since I was born (waiting times, stop, go, stop, go, smelly people, etc.)

I was thinking about this. I buy a Bicimoto I showed you all in the beginning of this thread, and later I'll try to install a Honda engine, but with a chain, not friction drive.

Do you think that will save me more money on maintenance than HT engines? Since Honda engines are of a much higher quality...
Consider I'm thinking cheap on the overall aspect. Fuel, engine price, maintenance. Doesn't matter if my HT engine breaks every month, as long as it's the cheapest motorized vehicle option. If a Honda engine is cheaper on the long term, then I'll go for it.

 

[Mike B]

That sounds like a good plan. Get the bike with the happy time and if it breaks you already have the sprocket and a rack mount 4 stroke chain drive would be easy.

 

[Al.Fisherman]

I'm just trying to be nice and imform you of the obvious, see these nuts have caps. You couldn't over-tighten them unless you were a gorilla on meth.

Buying a $60 tool you don't need-priceless.

I have news for you, these CHEAP acorn nuts have a thin top, and you can break through the top of the nut with less then the torque specifications.

One cap (on the left) broke off before I got to 50 inch pounds, the other (right) held to a 200 inch pounds. All hardware is stock that I've discarded.

This might be the worse advice ever given in one of these threads. Many times in what I'm sure is a cost cutting move the Chinese do not tap the holes all the way to the bottom. This leaves the threads sticking out further than designed. When you run those chump cap nuts down they can falsely bottom out. Keep reefing on them you will pull the threads right out of the block then you get to deal with that. One of the very first pieces of advice I read was to get rid of the cap screws and buy real hi-grade nuts. I bought the sick bike parts head stud kit, two sets to be exact. One in 6mm and one in M8 1.00 for 66 cc motors.

Telling someone not to use a torque wrench on a cylinder head flys in the face of over 200 YEARS of torquing heads down starting with steam engines and continues on to today. To the point of major motor manufactures use a torque device that torques ALL the nuts at the same time. Talk about an even pressure. Do it without a torque wrench and you have no idea in **** what torque you have at all.

$60? I said nothing about an S&K torque wrench. I bought my 1/4" beam type 25 years ago at a used tool shop for $7. They don't have to be exact, just have to read the same every time.

For a proper head gasket seal you don't just torque to the specified torque from the start, you go up in stages. I start the M8 nuts at 2.5 ft lbs and go up 2.5 lbs at a time until I reach 12.5 lbs. You also don't go in a circle around the head tightening the nuts. I use a "Z" pattern or you can also use a "X" pattern. Failure to do this can cause the gasket to leak. You will know it's leaking when black oily crud is coming out from under the head. Ignoring this will cause what is called "torching". The hot exhaust gasses will burn a groove or tunnel out of the cylinder, ruining the head or jug. The head can be saved by doing the glass & sandpaper routine. Torched cylinders are toast, you then need a new one.

After a motor has been run a bit you need to check the torques on the head. Do this when the motor is cold. Hot torques can vary wildly when rechecked cold.

Right on...EXACTLY why I bought a inch torque wrench vs using my foot pound torque wrench. They are NOT just for the head nuts, but used for the intake/exhaust and engine mount nuts...Ever think why I have NEVER had a stripped hole/nut or stud...I upgrade studs, nuts, and TORQUE to specifications. Those of us that do it right won't have to do it again...makes me wonder why this and in other forums are flooded with "I broke a stud"

Do you think that someone that doesn't know about a torque wrench, or torquing would have a feel for 60 inch pounds on 6mm and 200 inch pounds on 8mm..... Not even considering that ALL HT needs the heads milled. I have NEVER seen one that was flat.

 

[Wippenshox]

That sounds like a good plan. Get the bike with the happy time and if it breaks you already have the sprocket and a rack mount 4 stroke chain drive would be easy.

Do you think that I'll be spending less with a Honda, on the long term?

 

[Diver]

I have news for you, these CHEAP acorn nuts have a thin top, and you can break through the top of the nut with less then the torque specifications.

One cap (on the left) broke off before I got to 50 inch pounds, the other (right) held to a 200 inch pounds. All hardware is stock that I've discarded.

Wait- the only time you broke a nut (because it was "cheap"- gotcha) was by tighten it with a torque wrench. I don't get this- is this a joke?

The manual says to tighten using 10-12 lbs/inch. That's hand tightening, fellas. No need for the heavy industry..

 

[gubba]

whip........
i have built 30 or moe china girlsn from stock kits for my customers.
i have seen motors that did not last more than 500 miles and were trash.
buying a kit with a honest warranty from a known source replaced those few trash motors.

on average...... i see a my customers motors last 3500 to 5,000 miles. i have seen over 9,000 miles on several motors.
i put tons of miles on MY motors (pulling a trailer) and average 2 motors a year. i can buy a 'motor only' for a little ove $100. $200 a year expense is something i can live with.
ALL OF THE ABOVE....
is based on proper break-in and care. these ARE NOT racing motors. constant WOT, high revs and not enough oil will usually result in short life. check nuts and adjustmets daily during break-in and at least weekly thereafter. i double-nut all mounts, motor, exaust and intake mounts.

i throw away the provided 'bicycle chain' and replace it with a 415 chain.

advice is free! you can take or discard any of it.

stay dry

gubba

 

[biknut]

I'm just trying to be nice and imform you of the obvious, see these nuts have caps. You couldn't over-tighten them unless you were a gorilla on meth.

Buying a $60 tool you don't need-priceless.

This is called an acorn nut.

 

[Poopyboogin420]

I'm just trying to be nice and imform you of the obvious, see these nuts have caps. You couldn't over-tighten them unless you were a gorilla on meth.

Buying a $60 tool you don't need-priceless.

I bet I could over tighten them while on meth... I bought a torque wrench at a garage sale for $15. Just sayin'.

 

[gubba]

i found inch pound toque wrenches for $14 and up at amazon.com/automotive

gubba

 

[Diver]

This might be the worse advice ever given in one of these threads. Many times in what I'm sure is a cost cutting move the Chinese do not tap the holes all the way to the bottom. This leaves the threads sticking out further than designed. When you run those chump cap nuts down they can falsely bottom out. Keep reefing on them you will pull the threads right out of the block then you get to deal with that. One of the very first pieces of advice I read was to get rid of the cap screws and buy real hi-grade nuts. I bought the sick bike parts head stud kit, two sets to be exact. One in 6mm and one in M8 1.00 for 66 cc motors.

Telling someone not to use a torque wrench on a cylinder head flys in the face of over 200 YEARS of torquing heads down starting with steam engines and continues on to today. To the point of major motor manufactures use a torque device that torques ALL the nuts at the same time. Talk about an even pressure. Do it without a torque wrench and you have no idea in **** what torque you have at all.

$60? I said nothing about an S&K torque wrench. I bought my 1/4" beam type 25 years ago at a used tool shop for $7. They don't have to be exact, just have to read the same every time.

For a proper head gasket seal you don't just torque to the specified torque from the start, you go up in stages. I start the M8 nuts at 2.5 ft lbs and go up 2.5 lbs at a time until I reach 12.5 lbs. You also don't go in a circle around the head tightening the nuts. I use a "Z" pattern or you can also use a "X" pattern. Failure to do this can cause the gasket to leak. You will know it's leaking when black oily crud is coming out from under the head. Ignoring this will cause what is called "torching". The hot exhaust gasses will burn a groove or tunnel out of the cylinder, ruining the head or jug. The head can be saved by doing the glass & sandpaper routine. Torched cylinders are toast, you then need a new one.

After a motor has been run a bit you need to check the torques on the head. Do this when the motor is cold. Hot torques can vary wildly when rechecked cold.

Yeah, you're right. You need a Torque wrench for the head. I started having strange "slapping" noises and was told that I could have nuts may have been unevenly tighten, so I got a $10 schucks/O'Reillys TW and got busy- it went away. OOOOPS!!

I was wrong!!!!!

 

[rustycase]

W, your english is just fine! Far better than many I've seen on various boards.

Since your best option is a bicycle, I would advise you get the honda GX35 or the 50cc one they make. They are 4 cycle and your odds of a long life are far superior to that of the HT class of engines.

Depending on your terrain, a jackshaft shifter bike might be the best way to go.

Good luck
rc


...I guess I fly in the face of 200yrs of conventional wisdom... I don't use a torque wrench on many little things around an engine.
Yes, I'm very cautious, clean my threads, run a tap through machined threads on engine blocks, always use never seize type products, and definitely use a torque wrench on all critical assemblies when building new.
I would check for loosening and bolt stretch probably almost every time I rode a new HT powered MAB, probably without the torque wrench...
Oh well!

 

[socialdistortionkid]

As far as reliability goes and if money isnt an issue i would buy a 4 stroke engine kit. Just gas it up and go, no more mixing oil. Much more reliable than the 2 stroke engine kits that are sold. Little to no vibration on a 4 stroke and its pull start.

Only downside is the 4 stroke engine kit is about 3 times the price of a 2 stroke engine kit. If you have the money get the 4 stroke. You can save alot of money by building the bike up with the kit with your own bike versus buying an assembled bike.

http://www.bicycle-engines.com/49cc-belt-drive-complete-powered-engine-p-320.html