I Love My Two Stroke Bike

[GearNut]

Very nice pictures.
I have always been intrigued by 2 stroke porting. I understand what it does and how to go about doing it, I just have never done it before.
I have 3 engines now. I think I will have a try at it with one of them.
After all, If I bugger it up, a new cylinder is not that much $.

 

[Egor]

OK I got the bike running today, it is defiantly not a barn stormer. I don't like it at all. I don't remember them having this little power. I build the first one four years ago, and it did not take me long to get it running better. I don't think I would keep this hobby going if this is all I could have. I would like to find a high quality crankshaft, it would be nice to be able to get all the performance out of one of these engines. Have fun, Dave

 

[Egor]

I am off the two stroke, my love for them is waining. I think I will need some time off and find something to do for a while. I wanted to find a way to install a B&S in a bike, and I still have two of them on my bench. Have fun, Dave

 

[xlite]

OK I got the bike running today, it is defiantly not a barn stormer. I don't like it at all. I don't remember them having this little power.

This has been my experience too with all this porting and other hop-up baloney. In fact none had any noticeable effect except for the slant head and expansion chamber which did make a difference.

 

[Egor]

I have found that the head and expansion chamber has little affect on these engines, the reason being that you can not get the engine up to an RPM that will take advantage of the pipe. In the post I was referring to an engine that has no porting or any other mods, just stock. After I do the porting and the carb mods they are fine, I just wonder how everyone else gets along with a stock engine. I am doing a Honda PA50 and it is nice to work on an engine that will turn 10,000 RPM's with a few mods. Have fun, Dave

 

[xlite]

I have found that the head and expansion chamber has little affect on these engines

Dave, statements like that do not help your credibility.

 

[BarelyAWake]

I think he meant w/o any other mods - if so he has a point I agree with. Even "little" things like making the ID of the intake and exaust gaskets the same as their mainfolds, let alone making the manifoilds match their ports.

Should those things not be addressed - no, an expansion pipe would'nt make a big difference, it's too little too late in the digestive tract lol

I for one was pleasantly suprised and quite pleased how much the motor responded to a touch or two with the 'ol dremel. Very few other engines have such a profound change with so little work.

I blame that entirely on poorly matched components. Still - it's satisfying to be able to feel the effect of your experiments so easily

 

[xlite]

I think he meant w/o any other mods - if so he has a point I agree with. Even "little" things like making the ID of the intake and exaust gaskets the same as their mainfolds, let alone making the manifoilds match their ports.

The slant heads made a measurable difference in top speed on two of my engines and also the four I did for other people. This was before attempting any other mods and was measured with GPS on a slight incline.

On the other hand several subsequent experiments with "porting", drilling holes in the carb, filing plug electrodes, "upgrade" carbs, etc had no effect whatsoever. Noticeable or measured.

A recent SBP expansion chamber installation made a HUGE difference in pickup and top speed on one of mine. Again, not due to "placebo" effect.

These are observations made on bikes I built and tested. Not word of mouth. YMMV

 

[xlite]

The slant heads made a measurable difference in top speed on two of my engines and also the four I did for other people. This was before attempting any other mods and was measured with GPS on a slight incline.

On the other hand several subsequent experiments with "porting", drilling holes in the carb, filing plug electrodes, "upgrade" carbs, etc had no effect whatsoever. Noticeable or measured.

A recent SBP expansion chamber installation made a HUGE difference in pickup and top speed on one of mine. Again, not due to "placebo" effect.

These are observations made on bikes I built and tested. Not word of mouth. YMMV

I should mention that the only other thing besides slant head and expansion pipe that made a whit of difference was holes in the exhaust but that was not practical due to the noise increase.

About the only thing left to try is synthetic oil and that's next on the agenda.

 

[BarelyAWake]

Oh I'm sure you're dead on - but I was referring to actual porting & polishing, specifically enlarging and smoothing the intake and exhaust ports and their respective manifolds and matching their inner diameters. I'll be getting deeper into this engine later this winter.

This had a HUGE effect on my motor, from 27mph to 33mph sustained - 6mph is nothing to sneeze at for a lil dremel time and some properly made & sized gaskets. My SBP expansion chamber exhaust also had a profound effect, difficult to describe here though as it did little for my top speed, it's all get-up-and-go, which I'm more interested in at this point anyway.

I too use a GPS btw

On the other hand several subsequent experiments with "porting", drilling holes in the carb, filing plug electrodes, "upgrade" carbs, etc had no effect whatsoever. Noticeable or measured.

I haven't messed with the things you describe, keeping to more traditional mods I've done before with other applications. This whole "drilling holes in the carb" thing as an example, it seems odd and I've not heard it anywhere but here.

I didn't mean to infer that an expansion chamber hasn't an effect - I meant that if other, sloppy bits of the motor aren't taken care of first that effect would be lessened. If your engine kit had properly sized gaskets and/or slightly better castings - naturally such finish work wouldn't have as much of a result as it did with mine.

 

[xlite]

enlarging and smoothing the intake and exhaust ports and their respective manifolds and matching their inner diameters. I'll be getting deeper into this engine later this winter.

This had a HUGE effect on my motor, from 27mph to 33mph sustained - 6mph is nothing to sneeze at

I did open the gasket a bit and took as much off the round exhaust as I dared to match the square output port. No noticeable improvement. Same with trimming the piston skirt.

I suspect actually enlarging ports may have a significant power advantage. Using upgrade carbs would also probably start to make a difference in that case too.

After the slant and new pipe my engine starts to "scream" sooner so it feels like WOT is no longer the limit but max RPM is. I no longer run at full throttle like I used to but instead cruise and go up hills at half or 3/4. Now I have to back off long before full throttle unlike before.

In other words, no room for improvement power wise. At least not until I get a smaller sprocket.

 

[Egor]

I did not intend to have what I said come out negative. Sorry. I have built more engines than I can count. As a mechanic for the Honda Dealers in our area for over ten years, and still building engines as a means of making a living as an outboard mechanic, I can make a two stroke sing. I meant that the expansion chamber was intended for and engine that runs at RPM's that this engine most likely will never attain. The fact that it improved your engine is only because any exhaust modification would make the engine run better. As for the head if it improves the performance it is because it raised the compression, (obviously has a smaller combustion chamber). This being said for a head of proper dimensions the spark plug would always be in the center, this produces the best flame front reaching all points at the same time. Again for this engine to take advantage of this improvement it would have to be able to run in an RPM range that is not available. One easy way to determine if an idea is proper for this engine is to look at one of the high performance engines made by Aprilia or Yamaha, maybe a Van Veen, or MZ and identify some of the characteristics necessary to produce exceptional HP. I know you are getting some performance out of your mods, but these engines are so out of time, (I mean port timing) I just wish there was a way you could try one of my engines you would see what I am talking about. My engine will rev to max RPM's in half a second, and to flung to pieces in the other half. One of my race Yamaha's would go to 11,000 in the same time, still 50cc's. One telling thing about these little engines is the cooling fins. They are so small that with one of my engines climbing a steep hill in the area, half way up the hill the engine "heat soaks" and loses half the power when it starts to ping. A high compression head would only add to the heat problem. Examine any good two stroke engine and you will see the extensive cooling fins. I hope this helps with some of the problems that are out there. Have fun, Dave

 

[Egor]

Started a new build. This is the bike and no it is not a abandon bike from the park. LOL This one cost 160. I like the way it rides feels good, does not look comfortable but it is. It will be a challenge to get the drive chain to the rear wheel. I would like to install a 4 stroke kit on this but I don't have one I have an extra 2 smoke. I intend to put this up for sale, it will be new with a tested engine to make it reliable. The engine will have all my tuning done, with a guarantee that it will deliver the best performance. I will decide what it will cost after I determine the amount of time it takes to finish. Have fun, Dave

 

[BarelyAWake]

Egor - there is some truth in what you have said, but it's a matter of scale. We're talking go-karts, you're talking Lamborghini. Both are valid.

It's true that these pipes aren't perfectly matched, that these china engines aren't high-end performance, that there is much room for improvement and that improvement is limited. In some ways that's exactly what I like about them.

I love takin' a hundred dollar motor apart and seeing what I can do with it. Whatever marginal increase in performance I can manage to squeeze out of it makes me giggle. If I do manage to gain a few mph - it's a small triumph, it's satisfying to take a POS and make it scream.

If I was interested in true performance, if I wasn't just diddling around with toys - I woulda bought another motorcycle. I have less money in my entire build and all it's mods than what just one "good" motor would cost, I also know when I dust mopeds - it's all me.

I'm not particularly offended BTW, I'm just sayin'. There's really little room left for improvement on a Honda or Yamaha and I'd hate to crack the case on a new Yamamma and randomly experiment with my dremel.

*shrug* These are toys, no need to get all serious about 'em lol

 

[Egor]

Took the bike out for just a ride, I like this bike a lot. I was building a Recumbant and now I think I will abandon it. If I were to put a backrest seat on this bike it would be all I would ever want. I am still going to install an engine, I am working on the mounts, I have not come up with anything yet. Have fun, Dave

PS:I found a pic of a new work bike. LOL

 

[Junster]

Oh man that pic is just too funny

 

[Egor]

I wonder if he went to the market and when he came out the front wheel was missing, and just improvised the cart to get home. I think it would work OK if you were to tie the goose neck to the cart so the bike could lean in a turn. Have fun, Dave

 

[Egor]

Well I am putting the last engine back together. I gave up trying to get the crank trued up. I carved the cavities in the removable portions and at least got them even. As I was installing them back on the main section I put the whole mess up on centers to see how true it would be, guess I should have known how bad it would be. the one side was .037 out and the other was bumpy at about .008. the screws that hold it have a lot of play so I left them snug and took a hammer and gave it a whack on the high side and put it up on centers till I got it close. This will just have to do. I made my own gasket for the center section that is the part that was leaking in the first place. This thing has a wrist pin is for a 48cc engine so it is short and flops side to side. The bosses in the piston are short and the needle bearing can just about move out of the rod. This one had the noisier gears and it shows up that the center of the clutch is too small and the gear can move away from the drive gear, I checked to make sure all the bearings are in there, looks like they are there. These two engines are the ones that they missed milling the top of the cylinder so it holds the head out too far. And the head has the large combustion chamber, so the compression should be kinda low. I need to set my mill up to cut the top off, I have another barrel I can run in the meantime. I have been cutting the heads on my lathe, so I will get that done tomorrow. Ill keep you posted. Have fun, Dave

PS: I think the next engine is going to be a Spooky Tooth.

 

[Egor]

I guess I don't love my two stroke as much as I thought. I got one of the 4 stroke kits. I need to get a bike to install this thing on, the only bike left is my wife's. I hope she is not looking at these posts, or I'm in trouble. She will never know she hasn't ridden that bike in over 15 years. She'll never notice. I'm trying to make this engine look good, instead of looking like a large weed wacker. I may run it without the fan cover, I already threw the fin shroud away. I would like to find a SS mixing bowl that would fit over the flywheel and make it look like an old Mustang bike engine. Have fun, Dave

PS: I am going out in the garage now to get that bike down from the rafters.

 

[GearNut]

I guess I don't love my two stroke as much as I thought. I got one of the 4 stroke kits. I need to get a bike to install this thing on, the only bike left is my wife's. I hope she is not looking at these posts, or I'm in trouble. She will never know she hasn't ridden that bike in over 15 years. She'll never notice. I'm trying to make this engine look good, instead of looking like a large weed wacker. I may run it without the fan cover, I already threw the fin shroud away. I would like to find a SS mixing bowl that would fit over the flywheel and make it look like an old Mustang bike engine. Have fun, Dave

PS: I am going out in the garage now to get that bike down from the rafters.

Thrift stores are your friend. You are sure to find a perfect mixing bowl or sauce pan to mod into a Mustang "flywheel".