New build...HF 79cc in a Trek

GoldenMotor.com

jbcruisin

Active Member
Oct 10, 2008
1,118
7
38
Lebanon, Pa.
Hey Scotto, I rode the Davis' brother's HF Q matic at my rally in August. I think it was Jim's bike. I liked it a lot. I had it up to 45 mph & it took off great from a stop. I am thinking of building one. I'm sure you'll like yours.
Jay
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
Thanks all, she's coming along rather well....

Here's the swivel for the throttle linkage I was talkin bout SB and a little heads-up if you're using the variable pulley up front. I modified the EZM cover to accomodate the wide shaft (which had to be trimmed about a half an inch) and the variable sheave using a 2-1/2" hole saw.....easy, simple mods. Also, notice the trimmed choke lever....mo betta! Here's the pics for the day





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scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
A couple more pics for good measure....





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That should about do it for now.....dnut
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
Very nice and clean throttle setup. I used the same spring arrangement on mine, anchored at the same spot and using the same left over spring from the original governor. I like your slotted bolt head at the throttle itself. Is that some kind of standard hardware item or something you modified to fit? My own efforts yesterday were in trying to re use the same wire linkage rod which had gone back to the governor. I thought about reusing it simply because it already fit into the throttle control and is something to be discarded otherwise. Connecting the rod to the new throttle cable is the interesting part. I've figured one way, but am looking to do something even simpler if I can figure it out. It is so interesting to see how people answer the same problems with different solutions. You and Elmo have steered me toward keeping it straightforward and simple. My anchor on the seat post will be another seat post clamp spread open to fit around the frame and then closed up again with a small bracket coming off it to house the cable adjuster. Thanks to your example I found one on an old caliper brake (two actually so that I would have a second nut).
Are you planning to make another plexiglass cover for this tranny? Thanks for the heads up regarding the cover modification. I wonder, too, if the mounting holes for the cover could be slotted more so that it could slide out enough for clearance. Probably not enough room to make the slot long enough. Just a thought. This winter I want to experiment with making a copper transmission cover, possibly with part of it being see through. I like the idea of being able to see the inner mechanism at work. Machinery is interesting. I recall as a boy studying the old locomotives at the train yard in Ottumwa, Iowa... the connecting rods to the wheels were a great fascination. I think I first learned about mechanics from watching my Indian grandmother's treadle sewing machine at eyeball level standing next to it. As a little guy I would "help" by assisting on the treadle and could not help but notice the way the treadle went to a connecting rod to a wheel which had a belt on it that went up into more mysterious realms and ended up stitching material together up at the headworks. Machines were magic. They still are. And bicycles are still a marvel of machinery. a mechanical pony to ride away on. Ha! How good is that? I like your pony, Scotto.
SB
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
That little swivel is just like those used on the HS carbs....I just scavenged one off one of my old Walbro carbs I had sitting around. You can actually buy them here: av914 , but the shipping would probably cost more than the part which is $2.00.





As far as a plexiglass cover for this one, probably not, but you never know. As far as modifying the stock EZM cover, you may be able to get away with just elongating the mounting holes....it would be very close for sure but there would also be a gap upfront between the cover and the base plate. The hole seems to be the way to go.

Can't wait to see your build, that's a really sweet old Schwinn frame!

Cheers, scotto-
 
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douglasseattle

New Member
Oct 5, 2010
24
0
0
United States
Why is the engine so high? Is it to clear the cranks? I have been thinking about this motor as well. I also thought about using 165 crank arms vs the typical 175cm. Not a lot of differnce but some
 

Fossil

New Member
Mar 15, 2008
228
2
0
Guthriesville Pa
The engine needs to be high in the frame because the cylinder slants back rather than straight up. If it sits too low, the cylinder will hit the seat post and the front of the engine will hit the down tube. It's just a matter of clearance. Get a wide pedal crank too. I have one and I think I'm still going to get pedal extensions too. It is a wide motor.

Jim
 

jbcruisin

Active Member
Oct 10, 2008
1,118
7
38
Lebanon, Pa.
The engine needs to be high in the frame because the cylinder slants back rather than straight up. If it sits too low, the cylinder will hit the seat post and the front of the engine will hit the down tube. It's just a matter of clearance. Get a wide pedal crank too. I have one and I think I'm still going to get pedal extensions too. It is a wide motor.

Jim
Last time I was at Quenton's he had pedal extensions.
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
Why is the engine so high? Is it to clear the cranks? I have been thinking about this motor as well. I also thought about using 165 crank arms vs the typical 175cm. Not a lot of differnce but some
This engine sits so high that the stock crank arms (175mm) will clear with ease. With the wide bottom bracket spindle and the wide (dog legged 165mm) steel crank arms, the pedals sit out past this 24" wide-screen monitor I'm typing on. Will be pedalin like the "checkerboard squarecrow", if ya know what I meanlaff
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
Will be putting some of the finishing touches on this build today.....fingers crossed....and should be test riding it before the Great Pumpkin arrives if all goes well....and it should. Stay tuned.dnut
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
having a problem with the chain....

OK, got everything aligned and buttoned down tight, took her out for a test run and it feels like the chain is skipping some teeth on the sprocket at a regular interval. After stopping, noticed the chain is kinky....stiff link kinda kinky. Running the Q-matic on the HF with a 56t rear sprocket and a 415 chain. Would a #41 chain cure this problem? Anybody else ever expirience this? Any input would be greaty appreciated, thanks.
 
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MotorBicycleRacing

Well-Known Member
Jul 28, 2010
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Re: having a problem with the chain....

The MaxTorque clutch is sized for 41 chain.
I can't get 415 chain to even fit on mine

OK, got everything aligned and buttoned down tight, took her out for a test run and it feels like the chain is skipping some teeth on the sprocket at a regular interval. After stopping, noticed the chain is kinky....stiff link kinda kinky. Running the Q-matic on the HF with a 56t rear sprocket and a 415 chain. Would a #41 chain cure this problem? Anybody else ever expirience this? Any input would be greaty appreciated, thanks.
 

speedster239

New Member
Nov 26, 2009
43
0
0
Torrance, CA
Re: having a problem with the chain....

Thanks man....that's what I was thinkin....off to buy 10' of #41.
The build looks fantastic. In response to the scarecrow pedaling, all I can say is that rearmounting is the way to go. My motor is on a Trek 3700. When I was at the hardware store one day, a guy noticed my bike and the first thing he said was "Darn, aren't you supposed to put those motors on a crappy bike?". I told him I was glad I put it on a nice bike because it made the ride all the more enjoyable, and comfortable.


Also, where did you get your 56 tooth sprocket?
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
Re: having a problem with the chain....

The build looks fantastic. In response to the scarecrow pedaling, all I can say is that rearmounting is the way to go. My motor is on a Trek 3700. When I was at the hardware store one day, a guy noticed my bike and the first thing he said was "Darn, aren't you supposed to put those motors on a crappy bike?". I told him I was glad I put it on a nice bike because it made the ride all the more enjoyable, and comfortable.


Also, where did you get your 56 tooth sprocket?
I believe that sprocket came from Spooky Tooth....the 56 tooth on my other bike came with the EZM kit, but I enlarged the hole to bolt it on a freewheeling HD hub.
 

speedster239

New Member
Nov 26, 2009
43
0
0
Torrance, CA
Re: having a problem with the chain....

I believe that sprocket came from Spooky Tooth....the 56 tooth on my other bike came with the EZM kit, but I enlarged the hole to bolt it on a freewheeling HD hub.
Great, thank you very much. I'm in the market for a bit of light-duty offroading and the 28t of course and even the 41t sprocket I have don't cut it on the steeper grade hills. I need raw low end power. Thanks again.

A heavy duty axle might be the way to go in this situation now that you speak of it.
 
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silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
Scotto,
You're keeping me in suspenders. How does the Greyhound build ride? How's it compare to the HS Black & Blue build?
I'm still at the fitting of tranny to motor stage on my 51 Schwinn. Dang that's a wide motor. I was telling Jim Davis, who has one on a Schwinn Corvette that the Greyhound should have been called a Bulldog. Tall and sleek it isn't. Hoping to hear it has nice low end grunt so that with my 65 T driven sprocket my Bulldog can climb steep hills and still cruise around 30mph, not fast as a Greyhound, but tough as a Bulldog. Ha!
SB