BGF Hongdu/Solex

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cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
It takes a pretty high idle to disengage it. The first time I got mine to kick out, I had to stop the bike with the brake while holding the idle up, it tried to choke out, I just kept adding throttle and it finally started slipping. After you do this a few times the shoes must wear in now mine idles easily when I stop. Keep trying.
 

wayne z

Active Member
Dec 5, 2010
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It's a fine line to hit the right rpm but it's there. On mine, I pull the throttle in about 1/4-3/8 inch.
Try to find the rpm that just starts to pull, then let off the rpm just a tad.
 

wayne z

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Dec 5, 2010
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just took it for the first ride, runs ok, after it warmed up it went i'm guessing 15 mph. my clutch isn't working though, tried all rpm ranges i could and it never disengaged. if it dosen't free up i'm going to put another lever on it and use a cable to lift the motor when i stop.
If you do, you might contemplate hooking up the throttle the normal way, let go = idle, or both hands will be busy when you lift the motor.
 

wayne z

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Dec 5, 2010
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OK, Whose gonna be the first one to modify one of these into a frame mount Shouldn't be to hard to engineer a pulley to to replace the roller and a wizzer or simplex style driven pulley.

Ditch the tank, plastic and the flywheel fins, and this would make a sweet but slow board track style MB motor.
 

stevoh

New Member
Mar 14, 2011
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Virginia
my main concern with the chinese solex is longevity. but if i can get at least a year of reliable service out of mine, i'd say it was worth it. and i would get another. but who knows how long BGF will sell these at such a discounted rate? especially with the cost of gasoline on the rise. anyway here is mine, total cost of build well under $300. that includes the used bike, paint, a new cargo rack, and nickel and dime items like hardware and new brake pads.
I knew I could find this post again - I have been hesitating on the solex style motor because I kind of like my bike (it's not a particularly great one or fancy brand but it fits me well), and I figured it wouldn't be good to use the friction roller on standard mtb tires, but it looks like you did on your recent build, and I wanted to know if that is causing you any trouble at all? The tires in your pics have about the same rough tread pattern as mine, so if it's working for you....
Steve (new to motobiking but been doing a ton of research and ready to take the plunge - advice is sought and welcome).
 

Colony Five

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Feb 14, 2011
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I knew I could find this post again - I have been hesitating on the solex style motor because I kind of like my bike (it's not a particularly great one or fancy brand but it fits me well), and I figured it wouldn't be good to use the friction roller on standard mtb tires, but it looks like you did on your recent build, and I wanted to know if that is causing you any trouble at all? The tires in your pics have about the same rough tread pattern as mine, so if it's working for you....
Steve (new to motobiking but been doing a ton of research and ready to take the plunge - advice is sought and welcome).
Steve, if you haven't already, you should read this entire thread from the start. if you want to use the solex motor everything you need to know to put one on your bike from the perspective of someone who never has before is there. this was my first build ever. i can tell you that you won't find a kit that is as easy to install and as inexpensively as the hongdu solex. very easy to ride as well.

the only real hurdle is ordering one on the cheap from BGF (the lowest price around for one) and having it arrive with no damage and working, as there is no warranty or exchange. as long as you can get past that, you are virtually guaranteed a successful build.

the bike i used isn't anything special either, just a wally world kind i picked up secondhand, and perfectly suited for a budget build like the hongdu. as for the tires, yes they are knobbies. so far they have been working fine, but i know they aren't ideal-the roller doesn't contact as much of the tire as it could or should because the center lug of the tire prevents it. i can see wear in that center lug already and i'm not even through the first tank of fuel yet. it will probably work better as the lug wears down, but then the integrity of the tire is somewhat compromised. not having used anything else, i can't really compare the knobby tire performance to something. i do plan to get a more proper tire for a friction drive eventually-perhaps you may want to wait and see how the knobby holds up and what i have to say about it later, but these things are just too much fun to let a little detail like tire type hold you up!
 
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Colony Five

New Member
Feb 14, 2011
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OK, Whose gonna be the first one to modify one of these into a frame mount Shouldn't be to hard to engineer a pulley to to replace the roller and a wizzer or simplex style driven pulley.

Ditch the tank, plastic and the flywheel fins, and this would make a sweet but slow board track style MB motor.
not me! i like mine the way it is so i'll leave that to one of you guys.

actually, i want to know when someone is going to take one of the HT motors and use it for a friction drive.
 

camlifter

Active Member
May 4, 2009
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acme labs marion ohio
i've got my throttle so it's at idle when you pull the lever in. don't want to have to hold it all the time when riding. set up this way i don't see any way to adjust the idle. just by pulling the lever in less than all the way i tried to get different idle speeds to release the clutch and couldn't find the sweet spot. i'll keep trying. ran pretty good though and i really like the look of it on the old western flyer. looks almost period correct.
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
On the subject of tires, I just got the wheels finished on the Velosolex basket case. I ordered and installed new original tires, 19x1.75. Looks like the thing was still on its original tires, and they werent that bad except for dry rot. Still had a good bit ot tread. This thing had to have seen some use because the front wheel was covered in exhaust residue. So it appears tire wear in not a major issue with a smoother tire. I converted a mountain bike to road tires. They were 26x1.75 and a smooth rounded profile, perfect for the Hongdu. Might have a look at em next time you need tires.
 

stevoh

New Member
Mar 14, 2011
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Virginia
Steve, if you haven't already, you should read this entire thread from the start. if you want to use the solex motor everything you need to know to put one on your bike from the perspective of someone who never has before is there. this was my first build ever. i can tell you that you won't find a kit that is as easy to install and as inexpensively as the hongdu solex. very easy to ride as well.
Thanks for the reply - I read the first 16 and last couple of pages, and actually owned a friction drive moped at one time - basically a McCullough chain saw engine on a kids 16" spider bike called an AMF Roadmaster moped, but it was rear drive.

The only thing I'm having a bit of difficulty visualizing is what do I do with my front brake? I have a full suspension mtb with the brake assembly mounted on a forward bracket in front of the forks by about 2.5 inches, which is about where I would expect the motor to sit. Moving the front brake doesn't look like much of an option the way the bracket is made, but that ain't necessarily a deal breaker either, because it just means this particular bike goes electric and I pick up a used cruiser with 1.95 tires to add the hongdu/solex motor to.

Another newbie question on the roller assembly, if anyone has time to run with this:

The Roadmaster I mentioned above had a VERY similar corundrum(sp) roller keyed to the crankshaft as well, and it got banged up pretty easily on rougher roads/trails; I recall replacing it several times (and it was quite the chore). Is the hongdu/solex roller assembly a bit sturdier?

Note that I'm not planning any serious off road usage, but would like to follow my wife around on her little Peace 4x2 on "end of county maintenance" type gravel roads and may be concerned about the hongdu/solex holding up?

Thanks for your patience, folks, I tend to overanalyze things like this before plunkin' down a coupla bills on unfamiliar territory.

Steve
 
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Colony Five

New Member
Feb 14, 2011
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Steve, the kit bracketry as it comes most likely won't fit your suspension fork and you'd have to fabricate a bracket yourself and possibly modify parts of your fork or get a rigid fork for your bike (or a whole other bike like i did.) i kept my front brakes by mounting them behind the fork, but i can't say whether that would work on all of them, but you really don't need the front brakes. you gain engine compression through the roller on the tire that helps act as a brake if you kill the engine and let out the compression lever. these points are addressed in more detail elsewhere in the thread.

as for riding in gravel, that is the sort of terrain that mine really hates, but that is probably because of my knobby tire. a lot of slipping in the gravel and on the roller like that. it still works, but just isn't as good as a paved or even dirt road. a better tire should help.

i want to note that the kit is mostly intended for a cruiser style bike. it will work on other types obviously, but you'll encounter a few minor quirks. nothing that isn't easily dealt with though.
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Some insights. Recieved my junk original motor. In comparing the Solex/Hongdu, there are differences, close but not the same. The original piston is ported differently, different timing and the holes are bigger, intake port in the cylinder is slightly bigger on the original. The piston in the HD is slightly larger, wont fit the Solex cylinder. The rings appear different, the original appear to have more cross section(were stuck could not measure). So they have made it difficut if not impossible to mix some parts. The external parts fit, cylinder fits also. Have not yet checked the rod pin to see if the rods will interchange. My original thoughts were to run an original Cyl/piston/rod. So, if replacement parts are needed Steves Moped is the place, he is selling the BlacknRoll/Velosolex parts, which should be compatible. VeloCruz I believe sells qriginal stuff. Also if the piston pictured in Steves parts listing is what you get, then it is like the original but for thr HD. So it appers there may be 2 versions of the engine, ours is somewhat de-tuned.
 

Colony Five

New Member
Feb 14, 2011
63
0
0
Southwest
Some insights. Recieved my junk original motor. In comparing the Solex/Hongdu, there are differences, close but not the same. The original piston is ported differently, different timing and the holes are bigger, intake port in the cylinder is slightly bigger on the original. The piston in the HD is slightly larger, wont fit the Solex cylinder. The rings appear different, the original appear to have more cross section(were stuck could not measure). So they have made it difficut if not impossible to mix some parts. The external parts fit, cylinder fits also. Have not yet checked the rod pin to see if the rods will interchange. My original thoughts were to run an original Cyl/piston/rod. So, if replacement parts are needed Steves Moped is the place, he is selling the BlacknRoll/Velosolex parts, which should be compatible. VeloCruz I believe sells qriginal stuff. Also if the piston pictured in Steves parts listing is what you get, then it is like the original but for thr HD. So it appers there may be 2 versions of the engine, ours is somewhat de-tuned.
thanks for checking that out and letting us know. kind of a bummer really, and if turns out that the blacknroll velosolex parts from steve's don't fit either, we are basically left with bastard motors without repair parts. i still think there must be a source for genuine (ha!) chinese internals that make repairs more economical. as it stands these are pretty much disposable engines as you'd most likely be better off just buying a whole new unit (barring any price increase.) so then how long one will last out of the box is an important issue to me, and it will be some time before we really know that...hopefully anyway!
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
All is not lost yet, when I get a chance later today I will measure the crank pin and rod length. If those are compatible then the Solex cyl/piston/rod will work. That should mean an increase in power and longevity. These parts are fairly cheap used and not too hard to find. Just means that there hope to keep the HD running long term. Who knows the HD may last as long the Solex. Its such an archaic understressed design maybe even the Orient cant secew it up too bad. About the BnR not being sold, Steves will sell you one or more under the Velosolex label, no problem.
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Heres a pic of the pistons, the difference is obvious. I measured crank pin/ wrist pin centerlines, crank pin throw and crank pin dia. and they are the same. So, the respective cyl/piston/rod assemblies are interchangeble. Look at the piston @ Steves and you will see it looks like the original. I dont think we got bastard engines just the domestic version. If you have one of these on a bike in the homeland, some high roller that coughed up for a BnR equivilent is gonna smoke ya.
 

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wayne z

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Dec 5, 2010
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Hey C-ball, do you think that the ports in the piston and cyl. of the HD could be easily modified to match the Solex?
In the u-tube clips I've seen, they seem to be faster than 20 mph and the get to top speed rather quickly
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Im no expert on 2 stroke tuning, maybe some one will chime in here, But, the Hd piston has the ports lower I dont know how you could raise them with out welding them up first. The simplest thing is to buy the BnR piston, IF what is in the pic @ Steves is what you get. Visably it looks like the original Velosolex. I havent looked closely at the cylinder ports yet could be the same and the have detuned the engine via the piston. Thats why I favor swapping the piston/rod assb. from a Solex
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
One more point, I got the original muffler with the junk engine. The small outlet pipe extends 3/4" from the muffler body. The HD is 2.25" I dont know if this is critical, but it may be a way to tune the engine. I am inclined to trim it. Thoughts?