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Motorized Cruiser Bicycles The beach cruiser has always been great bicycles to motorize. They just look good with a motor. Use this section to share and discuss about motorizing this classic.


4 stroke motorized cruiser

The beach cruiser has always been great bicycles to motorize. They just look good with a motor. Use this section to share and discuss about motorizing this classic.


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  #1  
Old 09-24-2011, 08:53 PM
jt1111 jt1111 is offline
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Default 4 stroke motorized cruiser

Hi all,

I have been lurking around here for a couple of months thinking about building a motorized bike. I think I am going to build a 4 stroke cruiser and I wanted to get some input before I started buying parts. I think I am going to start with a chinese motor b/c of the price, and I would really like to use SBP's jackshaft setup. It looks really sweet. My main goal is to use the bike as a commuter to work, about 13 mi. each way, so it has to be reliable and would love it if it cruised at 30 mph, not sure if that is possible. I want it to be quiet and ideally clean running, which is why I am leaning towards the 4 stroke setup. With that in mind,

1) is it foolish to use the chinese motor, should I use the subaru or honda.

2) Will the SBP jackshaft work with the 4G transmission?

3) Regarding the bike itself, there are lots of cheap cruisers out there, but I hear people talking about replacing wheels, etc. Is it cheaper in the long run to buy a nicer (say Felt) cruiser or does a cheaper one suffice. I see lots of nice looking cruisers for around $200 give or take.

4) Brakes: I am going to use a disc in the front and probably a V brake in the back. I am not going to bother with a coaster. Does this change the thoughts from above.

Any other advice would be greatly appreciated. thanks,
jt
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Old 09-25-2011, 05:15 PM
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The_Aleman The_Aleman is offline
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Default Re: 4 stroke motorized cruiser

Welcome to the forum!

1) All the 4-strokes are heavy duty compared to the typical 2-stroke that's used. The chinese 4-strokes are copies of Japanese industrial engines, usually Honda, so they are quite good for a "made in China" motor. I have one and it's a little underpowered compared to the Honda GXH50 it's copied from, but it's reliability amazes me. It has needed nothing but fuel and an occasional oil change for the most part in 13 months.

2) Yes, but there are 2 different 4G boxes. The "Honda" 4G is narrower and pretty easy to run on the SBP 4-stroke shift kit. The regular 4G has a domed clutch bell and is roughly 1.5" wider. You might run into crank arm/pedal clearance issues using the wider 4G. Custom arms can be made to solve this.

3) Starting with a good bike is ideal of course. Cheap new bicycles have generic components which will likely cause you problems down the line. Many members here will agree that it's better to buy a quality used bike than a generic new bike.

4) You cannot use a coaster brake with a shift kit anyway. No loss there!

Best way to accomplish a shifter 4G:

Start with a bicycle with good brakes, 5-8 speed external shift or 3-14 speed internal shift. Must have enough room for a 9.5*9.5*9.5 box in frame.
Buy Honda GXH50 or Huasheng 142F with "5/8 shaft"
Buy Honda 4G standalone
Buy SickBikeParts 4-stroke shift kit
Then you need throttle and fuel tank.

Finished example:

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Old 09-25-2011, 09:03 PM
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wayne z wayne z is offline
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Default Re: 4 stroke motorized cruiser

Wow, that's great advice , and a great example in the photo :~)
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Old 09-26-2011, 02:01 PM
jt1111 jt1111 is offline
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Default Re: 4 stroke motorized cruiser

Aleman, thank you for the fantastic reply. Lots of good advise in there and exactly what I was looking for, of course answers bring about more questions.

I have been looking at a Firmstrong, Fito, or Micargi type cruiser. Will these stand up to this setup? I am specifically worried about the wheels and whether they will hold up to the punishment.

Sounds like it is easier to buy the 4G transmission and motor separate, and then buy tank and other parts, rather than a kit. Does the jackshaft kit come with everything to mount the engine?

I have read that the hua sheng needs the output welded, has that been fixed?

thanks again for your help.
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Old 09-26-2011, 02:50 PM
showcaller showcaller is offline
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Default Re: 4 stroke motorized cruiser

Do not buy Firmstrong! They are junk. I know. I made that mistake nine months ago. I have replaced both wheels and tires. The brake gave out so I have installed front and rear brakes. I am buying/building a new bike. Haven't figured out exactly what bike I am buying new or building from scratch but I am going to install the new 4 stroke EZM kit that Heliobikes handles. (see their ad on the side of the web page) Remember, even if you buy new, you are still going to spend dollars upgrading various components, so in the long run you might very well be better off buying a decent used frame. I have spent more hours reading more threads and posts on this web site and the general consensus seems to be if you start out with a decent frame, you can build a decent bike. Remember, there is more torque placed on the frame with one of these engines than you think. I will never buy another frame made in China - end of story.

Good luck and know there are alot of people who frequent this website who know a whole lot about this stuff and are happy to share! Good luck!
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Old 09-26-2011, 04:15 PM
jt1111 jt1111 is offline
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Default Re: 4 stroke motorized cruiser

OK, thanks, I appreciate the feedback on the Firmstrong. From what I have read from blogs and such Firmstrong is supposed to be one of the better cruiser frames. I have no idea if that is true or not. I am not really familiar with cruiser frames, what brands are recommended? I live in a smaller area, so finding a used one may be difficult, especially because I want one that I can put a shift kit on. Are the frames different sizes (hub size) for bikes with cassettes or are the wheels an hubs just different?
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Old 09-26-2011, 10:40 PM
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The_Aleman The_Aleman is offline
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Default Re: 4 stroke motorized cruiser

Quote:
Originally Posted by jt1111 View Post
Sounds like it is easier to buy the 4G transmission and motor separate, and then buy tank and other parts, rather than a kit. Does the jackshaft kit come with everything to mount the engine?
Yes, the SBP kit has motor mount, cranks, sprockets, chains - just about everything you need. You will still need a tank, throttle, and 9/16" pedals. Depending on what type of bike you're using, you may also need a bottom bracket adapter to install the crank assembly. SBP sells it.

Quote:
I have read that the hua sheng needs the output welded, has that been fixed?
The 4G's output only "needs" it if it breaks, really. Another member here shift-kitted a 4G about the same time I did, and he's had to weld his output freewheel. He also puts many many more miles on his motorized bicycle than most of us. When he hit 12,000 miles on his setup, I had 1000 miles lol

I'm getting close to 3000 miles now and my freewheel is still holding up well. Another thing you may have to worry about is the clutch drum on the Honda 4G. It may need to be welded, and I recommend you get it welded immediately. It's a 2-piece unit that appears to have been pressed together, comes apart easily unless it's welded.

Installing heavier clutch springs at this time is also advisable, the stock ones are a little too "light", can cause early engagement and difficulty idling. Finally, another point of contention is the clutch bushing. The stock one is junk, and should be replaced with a real Oilite bushing. They are $2, get several.
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Howto: 49cc GXH50/HS/Titan valve adjustment

Pedaling harder is the cheapest speed upgrade
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