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2 Stroke Bicycle Engines & Kits 2 stroke engine kits need careful installation and setup, find out how from our professionals here!

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Old 09-16-2009, 07:07 AM
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silverbear silverbear is offline
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Default 2 stroke centrifugal clutch

I'm wondering if I can get some advise from any of you who have a HT motor with a centrifugal clutch. I will be mounting one today on my American and am confused about how this thing works. I am accustomed by now to less than adequate instructions/suggestions from BGF, but until now it didn't really matter. I can see that the clutch housing is different from the other 80 engines, but why is there also a clutch lever, cable and all the normal stuff they attach to on the engine? How can you have both a centrifugal clutch and a manual clutch at the same time? I thought it was one or the other. This motor has a pull start which I personally like (have one on my other American), but if there's a manual clutch that would suggest you could bump start it, but that doesn't make any sense to me. I admit I know little about clutches, but am I missing something here? I notice most of the sellers do not have an engine with this "automatic" type of clutch. Is that for a good reason besides economy? Any real pitfalls? Any suggestions regarding operation or maintenance? The PDF file provided by BGF gives no information at all about the centrifugal clutch, no schematic, no instructions. I wanted to try an automatic type of clutch on one of my bikes to see if it is something I want to offer customers in the future. Yes, I plan to build bikes for sale to augment my social security. I know that older riders and some women would be more likely to purchase a bike if it were easier for them to ride. We here on the forum are comfortable with manual clutches. Sometimes I forget there are people who have never used a clutch on anything... never drove a car with a stick shift. It may seem like nothing to us, but as you know we're all a little bit different here. In fact I've noticed that some of us are real different... Ha! Thanks for any advise ahead of time.
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Old 09-16-2009, 03:17 PM
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Tim_B_172 Tim_B_172 is offline
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Default Re: 2 stroke centrifugal clutch

You can still use the manual clutch because it clutches a different part of the gear train than the centrifugal clutch does. I assume you have had the gear cover off of a regular HT engine before. Well, the cent. clutch takes the place of the small gear where as the manual clutch works by basically coupling the chain sprocket to the big gear. The reason you might want both is so that you can rev the engine up to high RPM without going anywhere. That might come in handy when starting a cold engine and using the choke.

I bought a cent. clutch kit but opted not to install it. It would require me to make some permanent modifications to my engine that I don't really want to do. Also I'm afraid that it would slip when the engine is bogging down on the way up a steep hill and there are a lot of hills in my area.
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Old 09-16-2009, 06:55 PM
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silverbear silverbear is offline
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Default Re: 2 stroke centrifugal clutch

Quote:
Originally Posted by Tim_B_172 View Post
You can still use the manual clutch because it clutches a different part of the gear train than the centrifugal clutch does. I assume you have had the gear cover off of a regular HT engine before. Well, the cent. clutch takes the place of the small gear where as the manual clutch works by basically coupling the chain sprocket to the big gear. The reason you might want both is so that you can rev the engine up to high RPM without going anywhere. That might come in handy when starting a cold engine and using the choke.

I bought a cent. clutch kit but opted not to install it. It would require me to make some permanent modifications to my engine that I don't really want to do. Also I'm afraid that it would slip when the engine is bogging down on the way up a steep hill and there are a lot of hills in my area.
My internet was out today so I read your post after installing the new motor, an 80cc slant head automatic. I figured out that the manual clutch was needed and after test riding it for only a couple of miles I decided I like it. No slipping on hills so far, but I'll know better later this evening after more miles. Actually you can bump start it, too. I had figured you couldn't. So far anyway all is well and I like being able to come to a stop without clutching, giving it gas and taking off. If I lived in town with lots of stops and starts this would be the cat's meow. I always feel like I'm shooting craps when I buy from BGF because it is hard to communicate with Rick, but I have to say that after four engines I have had all good ones, quick shipping and the little difficulties (crooked idle screw, missing carburetor part) he took care of right away). So far so good. The engine was about $150.00 with shipping, so the price was right. I guess I'll keep giving the benefit of the doubt until I have reason not to.
By the way, my on again off again significant other, former wife of sixteen years and now girlfriend has been talking about buying a place in St. Joseph to spend winters there. Here in northern Minnesota it is brutal and endless. How do you like it there? I have googled the town and it looks like there would be some good places to ride. Are you the only one with a motorbicycle or are there others? What about the laws in your state and the local police? Any hassles?
Thanks again for posting.
Silverbear
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Old 09-16-2009, 07:39 PM
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Tim_B_172 Tim_B_172 is offline
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Default Re: 2 stroke centrifugal clutch

Hi Silverbear,

Glad to hear that the clutch isn't slipping, maybe I'll try it after all.

Saint Joseph is Okay, sometimes it seems like a "hick town" but then again I'm not originally from here. There are some really good riding places, we have a system of parkways that make for nice pleasure riding. I buzzed around one little loop of the parkway today in fact. The west side of town where I live has some massive hills though, so I always have to take that into account. As for other motorbicyclist's, as far as I know it's just me and my Dad. He is the one that got me into this actually, when he put one together to save gas on his daily trip to work. I can't really use my bike for work, my regular job involves driving a LOT and any part time work at the airport is across the river and I don't want to ride on the highway to get there. The laws here are pretty lenient basically anything less than 50cc, 3 HP, and 30mph is legal without a license plate. The cops don't even seem to care, I've ridden past plenty of cop cars and they haven't given me any trouble, usually they just stare like everyone else. Also if your significant other is thinking of wintering here, she should know that the winters here are not that great. We get ice and snow every year and at least 2 weeks straight of sub zero temps. I don't know what it's like in Minnesota, but if I were her, then I would go farther south.
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Old 09-16-2009, 09:30 PM
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silverbear silverbear is offline
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Default Re: 2 stroke centrifugal clutch

About the automatic... starts are not as snappy as a manual clutch. If you were at a stop sign and had to go uphill from there it takes a while for it to get going, so you peddle assist. I don't know that on a hill where you currently have to peddle assist it would be much different since you're still going to have to peddle. Might be a little slipping in that situation. I'll know better when I ride it more. I didn't go real far from home where the biggest hills are since I want to be sure all is right with the install and the engine. I'll let you know what I think. Where it would be great is for people uncomfortable with a manual clutch, for those who might be disabled, arthritic or that sort of thing and anybody who mainly rides flatland with lots of stops and starts. Once you are going up to speed, say fifteen or twenty it doesn't feel any different from the manual clutch.
Regarding northern Minnesota winters. The record cold a few miles from me is 63 degrees below zero. 40mbelow is more normal for the coldest. 20 below happens more frequently and it may be below zero for weeks at a time. First snow is mid October and ice breakup on the lakes is early May. It isn't just the severity of the winter, it is the duration that is so wearing. Spring is a couple days long and summer is a glory of cool air, hot sun, mosquitoes, thousands of lakes (Minnesota has over 12,500 lakes (at least 10 acres to be considered a lake), most of which are up here by the Canadian border. We have a pretty good idea of what to expect there in St. Joseph. Believe me, we consider that to be the banana belt, almost tropical.
That's good to hear about the police there. I make a point of obeying all the traffic laws, don't speed in town, use hand signals turning and have lights including brake lights. I want to keep these things untagged and uninsured as long as possible. If the public sees that motorbicycle riders are a cross section of people, most of whom ride responsibly maybe they won't condemn the whole idea of motorbicycles. Anyway, I'll keep you posted regarding the automatic. It is probably a trade off, with some things better and some not as good as manual. Actually that's true with cars, too.
Silverbear
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Old 09-16-2009, 09:53 PM
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Default Re: 2 stroke centrifugal clutch

auto cluchs are great ......Blakenstein
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Old 09-16-2009, 11:03 PM
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Default Re: 2 stroke centrifugal clutch

Auto cluches are great however......you cannot push start... if motor is idling too high while bike is standing still it will burn out ......if startup at high rpm bike will jump out from under you and you have to be quick to grab it.......from Blakenstein.
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Old 09-17-2009, 12:36 AM
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silverbear silverbear is offline
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Default Re: 2 stroke centrifugal clutch

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Originally Posted by Blakenstein View Post
Auto cluches are great however......you cannot push start... if motor is idling too high while bike is standing still it will burn out ......if startup at high rpm bike will jump out from under you and you have to be quick to grab it.......from Blakenstein.
What do you mean, "you can not push start"? You mean like hot dogging it, over revving the engine? Do you know of a reference anywhere on servicing, repairing these? How does yours do on hills? Any slipping?
Silverbear
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Old 09-17-2009, 12:09 PM
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Default Re: 2 stroke centrifugal clutch

I can't pull start my bike so I have to use the manual clutch and pedal up to about 8 mph before I engage the clutch then the auto clutch takes over, while I am still pedalling, to get the bike running. This seems to work just fine for me.

I guess you could think of the manual clutch as sort of like the "D" and "N" on a car. disengaged is "N" Not going anywhere. "D" is Drive manual engaged transmission spins tire.
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Old 09-17-2009, 12:54 PM
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silverbear silverbear is offline
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Default Re: 2 stroke centrifugal clutch

I just finished several miles riding with the automatic and find that I like it more as I get used to it. It is different to be sure, much like the difference in cars between an automatic and a manual transmission. And in the same way the bike feels smoother in operation. Where did you guys get your engines? Anybody have any written information on these, like the way you're suppose to use them, servicing and maybe a diagram or schematic of the inner workings? I got nothing with my kit to help me understand its operation. It came from BGF and I think that kind of information and communications gap is BGF's weakness. On the plus side was cheap price ($150.00 with shipping), fast delivery and I was happy with the kit. Everything was there and other than adjusting the idle I didn't have to do anything for it to run smoothly. I'm running Opti-2 in it. I don't think it has as much power as my other engines, but they weren't as strong as they are now when they were new, either. I took it up to 30mph for a moment or two, but have been pretty much varying the cruising speed from 15 to 20... speed up to 25, the down again. I give it all it has on inclines. I think that's the best for these when they're new... for the most part modest speeds, then work it some briefly and eat some some miles. I have only 25 miles on it so far and for a new motor it is really smooth. Who else handles 80cc HT automatics and what kind of experience have you had with the motor and with the vendor? About how many miles on the engines? So far I think this is a good rig.
Silverbear
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