BGF Hongdu/Solex

[cannonball2]

That question is often asked. In theory should work as well if the up right angle of the engine is maintained, mainly in regards to the carburator. The structure of most bikes has a sloping rear section so it would require some modification in this regards. Also the engagement/disengagement would have to be adressed behind the rider, maybe a scissor clutch could be used, for inital starting, and free pedaling. I am running the 2.125 tire on the front, it took some "washering" of the engine to keep it centered, but I find the larger tire to smooth the ride. I ride about 400' of gravel drive to the road and the difference between a tire of this size and a 1.95 is noticable. As long as the engine unit is mounted to the traveling fork it should present no problems. The front brakes would probably have to go unless relocated to the rear of the fork, and the fork bridge common on most suspension unit would have to be removed. A solidly mounted engine will serve the same porpose.

 

[cannonball2]

Hers a link to a rear mount. Silnik rowerowy Solex Hongdu wersja 3800 - YouTube

 

[Mike B]

Here's mine;

Works great!

Much more stable on the back and the heat and the noise are behind you -

 

[cannonball2]

Looks great! Its it pretty easy to raise and lower behind you?

 

[Mike B]

Nope, it's fixed. When I tried to raise it, it wouldn't move far enough to clear the tire. The muffler was holding it back.

In order to raise it I would have to remove the muffler, pull the motor back and run a bolt through the end hole of the slider slot.

I'm just gonna leave it fixed. Works great. Will run smooth at walk speed, hardly makes any noise. This is my neighborhood cruiser. Just pedal and off it goes. That cast iron cylinder takes a while to warm up though, you don't get full performance for like a half mile starting cold.

It's a hoot though and I really like it!

I have it geared real low, 36T on the pedal, 22T on the wheel, very nice for starting.

 

[cannonball2]

You came up with a nice clean install, I like it. In general my Solexes are cold natured too, take about the same amount of time before the choke can be fully released. Have any emergency disengagement proceedure in case of a far from home breakdown? It is amazing just how slow these things will run.

 

[Willy79]

Thank you Mike B for posting a picture of your rear mounted Solex. It is true that a picture is worth a thousand words. I love the clean way that you have mounted the motor over the rear wheel. You have answered the questions that I had about a rear mount. It is nice to have less noise and better stability with the motor weight not over the front steering wheel. My new build is going to be a rear mount.
I have just finished my second bike. I found a used Trek Navigator aluminum frame mountain bike with a 7 speed Shimano Nexus geared hub. It has front fork shocks and seat post shock and a wide adjustable height handle bar. I was able to mount the Solex in front of the front brake and keep the brakes as is. The bike has a much better ride and I don't feel every little bump. I will post pictures soon. I am still searching for a hose to use on the joint between the exhaust manifold and the muffler. The silicone hose takes the heat but not the oily exhaust. Has anyone solved this problem?

 

[Mike B]

So far, I have no oil coming out of the joint.

But, that's only about 10 miles and I'm running 50:1 Tanaka oil.

And since the oil is only going to blow backward, I don't care if it comes out or not.

Yeah, rear mount is cool -

 

[Willy79]

I need to find some TANKA oil. I have been using Pennzoil two stroke oil 32:1 and I get black oil splatter all around the muffler joint if it is not covered with a hose. I have a question on the Solex clutch. When mine disengages with the motor running. The motor gets very rough and noisy with what sounds like a lot of grinding. Is this normal for the Solex clutch?

I have attached pictures of the Solex mounted to a mountain bike with front suspension. I built two new motor mounting plates with the rear end attached to the brake mounting screws and the front end supported with a tube attached to the fork fender holes. I moved the springs to the outside to give more clearance for the tires.

 

[cannonball2]

I need to find some TANKA oil. I have been using Pennzoil two stroke oil 32:1 and I get black oil splatter all around the muffler joint if it is not covered with a hose. I have a question on the Solex clutch. When mine disengages with the motor running. The motor gets very rough and noisy with what sounds like a lot of grinding. Is this normal for the Solex clutch?

I have attached pictures of the Solex mounted to a mountain bike with front suspension. I built two new motor mounting plates with the rear end attached to the brake mounting screws and the front end supported with a tube attached to the fork fender holes. I moved the springs to the outside to give more clearance for the tires.

Very nice job on the Trek! After one tank @ 32:1 I moved to 50:1. There is very little if any oil blow at this ratio. This is the called for ratio for the original Solex engine. I have a silicone tube on the joint with many miles on it with no problems.
Concerning the clutch, mine had to wear in a bit. The engine idle was a little rough and dragged down until the shoes seated. Caused a bit of bucking or rattling, but no grinding as I recall. I speeded up the seating process with several sessions of increased idle with the bike stationary. Once worn in its a smooth idler.

 

[wayne z]

t There are things that can be done to make them run better. I bought 2 and they both ran poorly. I discovered that the heads needed to be shaved .100" to bring the compression up to tha Solex specs. The run fine now.

 

[wayne z]

I need to find some TANKA oil. I have been using Pennzoil two stroke oil 32:1 and I get black oil splatter all around the muffler joint if it is not covered with a hose. I have a question on the Solex clutch. When mine disengages with the motor running. The motor gets very rough and noisy with what sounds like a lot of grinding. Is this normal for the Solex clutch?

I have attached pictures of the Solex mounted to a mountain bike with front suspension. I built two new motor mounting plates with the rear end attached to the brake mounting screws and the front end supported with a tube attached to the fork fender holes. I moved the springs to the outside to give more clearance for the tires.

Try the Pennzoil at 50-1 That's what I use with no probs at all. I also have silicone hi temp hose on my muffler joint. I also cut my little tailpipe to 3/4" long and drilled a 5/16 hole in the bottom of the muff for slightly better performance.
Great idea abot moving the springs for tire clearance.
Could you not have enough pressure on the tire and the roller is slipping causing the noise?
The clutch don't disengage smoothly and easily until it has some time on it.

 

[Mike B]

Interesting.

I have thottled back many times and the speed will go down to walk speed but the clutch never disengages. I'll have to try that while braking to see if I can stop the bike and idle through the clutch.

I am in the process of re-routing the throttle and compression release cables below. I may have to do the head shave thing as I don't think I'm going 15 on this. But to tell the truth, 15 is fast enough and it starts so easy...

 

[cannonball2]

Interesting.

I have thottled back many times and the speed will go down to walk speed but the clutch never disengages. I'll have to try that while braking to see if I can stop the bike and idle through the clutch.

I am in the process of re-routing the throttle and compression release cables below. I may have to do the head shave thing as I don't think I'm going 15 on this. But to tell the truth, 15 is fast enough and it starts so easy...

The clutch has three functions. First is to engage at zero rpms to start the engine. Second is to disengage at a designed in idle speed, and third to re-engage as the rpm increases to drive the bike. The H/D carb seems to idle lower than the Solex, so it is below disengagement, therefore it will ride at a walk. If you speed it up just slightly it should disengage, and idle.
The original throttle set up is to default(handle not pulled) to wide open which is where the engine lives its life. When the throttle/brake handle is applied the carb is returned to a predetermined, by the barrell design idle. Its a really ingenious system. I had mine originally throttled in a normal fashion, pull the throttle lever for max throttle, relax for idle. It actually works better to start at WOT, and leave it at WOT and pull the throttle lever to return to idle. The original set up applied the brake at the same time the engine was returned to idle.

 

[cannonball2]

Re: BGF Hongdu/Solex Bike Bug Alterantive

If you are interested in a front wheel drive friction kit - check out our Improved Bike Bug - Google Bike Bug and it will take to our site.

USA Made 30 warranty - tested it before market - teenager ahd 5,800 miles in one year - no repairs. Plus engine can be removed from bike for safty or storage with no tools.

CBS did a news clip also that is on the site. Have both front wheel and rear drive models.

Thanks for the info on your product, it might be better placed in the swap and sell area. I believe most of the followers of this thread are interested in the Solex/clones because of their uniqueness. They are for sure not up to date on technology or power out put( they were designed in the late 1940s). What they are is one of, if not the most successful motorbikes/engines ever, being made into the millions. I guess similar to the VW Beetle. Their engineering is rather odd, but well thought out, and their durability is renown.
While I am sure your current product is well made and superior in performance, it is galaxies away in charm, which is why the Solex and it clones are so endearing.

 

[Mike B]

Thanks.

I have the throttle connected to a "shift lever" down on the frame like the old 5 speeds. Yes default is WOT.

Added a front caliper brake and have the rear coaster brake.

The compression release is on the handlebar with the front brake.

Compression release works great as a brake and to ease pedaling from a stop.

I will have to play with the throttle some and apply the brakes to see if I can get the clutch to release.

If not, it's not a big problem. I just love the sucker.

Especially using the comp release to slow down to almost 0 and then release and it just takes off.

Amazing -

 

[cannonball2]

Mike B: play with it a bit and you should find its sweet spot. There is no formal way to adjust the idle like a stop screw. Im using a brake lever as a throttle and originally used its adjustment to set the idle for the clutch disengaement. I later got hold of an original Solex carb and it idles at low stop as is. Maybe a 2 step setting would be cool as now mine wont do the idle at a walk, which was really cool. I never realized an engine could power a bike so slowly.

 

[wayne z]

To make the clutch disenfage on both of mine, I give it full throttle just before complete stop then let off until about half throttle.
Then once it brakes loose you can adjust hand throttle setting some to get it to idle. It takes about 1/4-1/2 throttle then to make it idle while stopped.
I have my handbrake lever throttle control set to full throttle with lever out.

 

[wayne z]

t There are things that can be done to make them run better. I bought 2 and they both ran poorly. I discovered that the heads needed to be shaved .100" to bring the compression up to tha Solex specs. The run fine now.

As I recall now, The head needed shaving .o40" to get Solex factory deck height. I shaved mine to .060 for just a little more performance.

Neither of my engines had hardly any crosshatch honing at all and the rings didn't want to seat. So I used a brake cyl hone annd de glazed the cylinders good. This made the rings seat well and improved performance .

 

[Mike B]

Took it out and verified that the clutch works as designed. At a little more than totally shut throttle I applied the brakes and stopped the bike and the engine still ran. At closed throttle it just dies.

Pretty cool.

Yeah, when I removed the head on mine the bore was very smooth and there were some very fine vertical scratches. The piston was covered with black oil, but was nicely chromed. It was obviously run for some time and not "new" as advertised. The only thing new in the kit were the levers, cables, muffler and hardware.

Never the less, I am very happy with it. It runs well, starts fast and easy, goes slow and makes very little noise.

Way cool for 60 yr old technology.

The motor might not have a lot of power (hey the carb bore is what 7 mm?) but the low speed torque is impressive. From putt-putt dead slow it just keeps putting right on up to as fast as it can.