Conversion of Chinese Belt Drive to 4:1 with Grubee 80T Pulley

michael whiteman

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I'm the guy Diesel Tech was referring to Mike. I bought a replacement 100T pulley because my original Chinese one had a huge wobble in it. The new pulley went right onto my output shaft with no sanding. This pulley will never wear out and you can get the belts anywhere. The problem you and I will probably have in the future will be not being able to get a replacement clutch bell with pulley. GruBee has a few but will not sell them to anyone but his previous customers. When they are gone there will be no more. Be kind to your clutch. You and I will end up getting a new tapered shaft engine when this happens. I doubt if there is a big enough market for someone to manufacture this then waiting for people needing replacements.
 

Mike St

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You
I'm the guy Diesel Tech was referring to Mike. I bought a replacement 100T pulley because my original Chinese one had a huge wobble in it. The new pulley went right onto my output shaft with no sanding. This pulley will never wear out and you can get the belts anywhere. The problem you and I will probably have in the future will be not being able to get a replacement clutch bell with pulley. GruBee has a few but will not sell them to anyone but his previous customers. When they are gone there will be no more. Be kind to your clutch. You and I will end up getting a new tapered shaft engine when this happens. I doubt if there is a big enough market for someone to manufacture this then waiting for people needing replacements.
You are so right. Grubee is about to corner the market and may be very difficult to deal with. At one time,
BoyGoFast carried some parts for the 15mm ebay kit but no more. Eventually, like you say, we'll all be
dealing with Grubee at very high prices.
 

UtiliD

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You

You are so right. Grubee is about to corner the market and may be very difficult to deal with. At one time,
BoyGoFast carried some parts for the 15mm ebay kit but no more. Eventually, like you say, we'll all be
dealing with Grubee at very high prices.
staton has far superior clutch bells with shafts you just have to swap out the bearings to fit a 1/2" or 5/8" shaft that is on the clutch bell then you can easily find t-belt pulleys 20t or smaller or larger to give you more options on gear reduction.(I would just double check the length of the shaft before buying bearings and the t-belt cog/pulley)
staton also has 9t-15t 410 sprockets(a quality 415hd chain is strong enough for this application and will fit the 410 sprocket) with a 15mm bore and 2 set screws.
they also have 15mm bore freewheel adapters(also with 2 set screws) in 30mm x 1 metric thread or 35mm x 1.0 metric/1.375 x 24 standard thread. So instead of the solid output sprocket or the garbage 11 or 12t output freewheel sprocket you could put a quality 1/8" freewheel as your outgoing/final/drive sprocket if your build has the room for it. You just want to make sure you get a right hand thread freewheel adapter if you go this route.

they actually have all these in several different configurations and different size bores. The site is a little difficult to navigate... the titles of the items are not spelled out the same from size to size so it may take trial and error in the search bar of the site to find what your looking for. for example

410 sprocket 9t 15mm bore
then you could try to search for a 10t by typing
410 sprocket 10t 15mm bore but it might not come up because they didn't include the word bore in the title for the 10t 410 sprocket with 15mm bore

the freewheel adapters are even harder to search for but as i said trial and error and you'll find it.
 

Mike St

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Today, I began installing the Grubee 80T pulley on the Chinese belt drive.
It was relatively easy, just a little sanding of the shaft and the inside of the
pulley and it went on. But a I ran into a problem: the belt I ordered
which was called out by bicycle-engines is too small, the Grubee
belt drive is slightly different than the Chinese drive, so I ordered
a larger belt. Inspected the drive, it was in good condition. Also
inspected the Olite bushing I installed and was surprised how much
lubrication seeps out of the bushing. Everything was in good condition.
I am excited about the final bike. After I finished, it
will be a very sweet 4 stroke, with a top speed of about 32 mph -
nice! It should be a reilable four stroke, for great cruising.
 

Nirve

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Today, I began installing the Grubee 80T pulley on the Chinese belt drive.
It was relatively easy, just a little sanding of the shaft and the inside of the
pulley and it went on. But a I ran into a problem: the belt I ordered
which was called out by bicycle-engines is too small, the Grubee
belt drive is slightly different than the Chinese drive, so I ordered
a larger belt. Inspected the drive, it was in good condition. Also
inspected the Olite bushing I installed and was surprised how much
lubrication seeps out of the bushing. Everything was in good condition.
I am excited about the final bike. After I finished, it
will be a very sweet 4 stroke, with a top speed of about 32 mph -
nice! It should be a reilable four stroke, for great cruising.
Good job dude!
I had the same issue with the belt but was able to adjust the tension with the spanner wrench and turning that eccentric cam
 

Mike St

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Well, after buying several more timing belts, I found they were too big,
so I completely loosened the chain to allow the cam to move about 1/16 inch
more which allowed me to install the 505-5M-15 belt, but it is very tight.
I'm concerned that the belt will cause excessive pressure on the olite
bushing I now have on the drive. I now believe the right length should
be 510. The question is can I expect the belt to stretch a little or should
I purchase the 510 belt? If it stretched just a little, I think it might work
in the long run. Any comments?
 

Nirve

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Sorry you are experiencing this issue. I have the 505 Belt and were able to get the tension just right with turning the cam. I wonder what’s different

1660838250920.jpeg


1660838276486.jpeg
 

Mike St

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I just finished testing the bike and it runs so smoothly. I believe I
hit the sweet spot as the engine at this ratio has enough power
to take off from a stand still and at higher speed the engine runs
at lower rpm and it's very quiet. I used the 80T grubee pulley
for 4:1 on the belt drive and 41T on the rear sprocket, for a top
speed of about 32. I believe this setup is reliable and could
cruise all day at 18-22mph.
 

Sidewinder Jerry

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I just finished testing the bike and it runs so smoothly. I believe I
hit the sweet spot as the engine at this ratio has enough power
to take off from a stand still and at higher speed the engine runs
at lower rpm and it's very quiet. I used the 80T grubee pulley
for 4:1 on the belt drive and 41T on the rear sprocket, for a top
speed of about 32. I believe this setup is reliable and could
cruise all day at 18-22mph.
32 mph at 6785 rpm, not bad at all 👍
 
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