BGF Hongdu/Solex

[cannonball2]

Look at the cylinder base gasket and see if its a copper sandwich type gasket. If so its thicker that the original Solex gasket. Just rebuilt one Hongdu using used Solex parts from my Velosolex project, a real power house realitivley speaking. The Solex uses one gasket top and bottom and the base is much thinner. The Solex heads are just about the same height as the ones Wayne has lathe cut. For what ever reason Hongdu severely lowerd the compression with the head and the combo of gaskets, all these gaskets are moving the head further out.

 

[wayne z]

I wonder if the French company that originaly contracted the Hongdu factory, requested the lowered compresson to discourage other buyers/sellers from dealing with these engines.
Then, when the French contractor recieved their engines, they could easily shave the heads or remove extra gaskets and have nearly the original power back.
Sorta like secret propiatary info to discourage others from using these engines.

There are 2 vendors in the U.S. that stock parts for these, search Steve's Mopeds for one and VeloCruz might be the other

 

[cannonball2]

Velocruz is where I got my parts, Jeffs a nice guy to deal with, he sells Euorpean parts, Hungarian NOS I would guess. Nice quality. Who knows what the logic is behind Hongdus thinking. Could be as simple a a new employee adding too many gaskets for a couple of weeks, too much trouble ro rectify, but great candidates for disposal in the distant markets. The head makes sense for poor fuel markets. The whole little engine is sort of a mystery. Gotta love em though.

 

[MB Dave]

Took her for a run today. 3.5 km each way then 2km each way.
Top speed went up from 25kph to 30kph on the flats. 4 stroking above 30kph, say going down a slight hill. I can live with that.

Ultra Copper Gasket maker is holding up. Will leave it in there as a kind of experiment to see how long it lasts. Keeping a close watch on it.

Did the mods recommended by Wayne. Opened up the two intakes for the air filter a bit with a round file. Drilled a 6mm hole in bottom of muffler. Took about an inch off muffler tip.

When drilling the hole in muffler the drill bit wrapped around some steel wool.
Would removing this steel wool inside the muffler help performance or better off just leaving it in there?

The cylinder base gasket appears to be the same thickness as ONE head gasket. Looks like it's made from the same green material as the head gasket.

Thanks for the tips on Vendors. Hope they post to Australia.

 

[MB Dave]

Also forgot to mention. Updated spark plug to a Champion L92YC.

 

[MB Dave]

Making head gaskets just in case the gasket maker goo doesn't work.

Does anyone know what the fifth little hole on top of the cylinder barrel is for?
The one between two of the bolt holes. There is even a hole in the gasket to accommodate it.

She seems a bit more livelier and zippier now. Puurrs along at 30kmh, sounds happy and content.

 

[cannonball2]

The little hole is for the compression release passsage. Nice job on the gaskets.

 

[Mike B]

I took the head off this weekend just for a look see and this motor has been run for sure. Bore was nice and smooth with some very fine verticle scratches. Piston was domed with a nice chrome top. Yeah, there is a about a tenth inch from the gasket surface to the chamber. Spark plug was black and oily.

Looks pretty good.

 

[MB Dave]

Took the head off again to measure the squish according to instructions on this site VeloSoleX S 3800 Cylinder Head
My squish was 2.35mm when it should be 1.5mm.
Got it to about 1.8mm for now.
Put one of my home-made head gaskets on and tested. No real difference in performance. Removed the gasket and put some gasket maker goo.
Will test again tomorrow.

 

[MB Dave]

Took her for a test run today. Max speed still 30kph (18.6mph)
So, drilled out the two air filter holes to 8mm ea.
Still no difference. Hits a brick wall at 30kph (18.6mph)

On another note. The clutch has started to work. Takes a bit to get used to the correct rev range where it engages/disengages.

Also, got a better look at the cylinder base gasket. And yes it is a copper sandwich type with green material in the middle.

 

[Mike B]

That's cool.

Does the compression release work good as a brake?

 

[MB Dave]

Got me some valve grinding paste. Took the head off again.(getting pretty good at this now). Lapped the decompression valve and took her for a spin. Again 30kmh (18.6mph) top speed.

Mike. I'm not sure about using decompression lever to brake as I have rear coaster brake on my bike. I think it acts more like a clutch than a brake. The only time I use the decompression lever is when starting and sometimes when shutting down. Most of the times I shut down the engine by letting it stall.

 

[MB Dave]

Ok. I feel a bit better now. No matter what I tried, could not get it to go over 30kph (18.6mph)
Found this data VeloSoleX S 3800 Engine Data
That states top speed is. Wait for it 30.1kph (18.7mph)
So gotta be happy with that.

 

[cannonball2]

That speed is for the 42mm roller I believe. There was also a 45mm fitted to various models at the same engine rpm(4000) I believe it produced 20.6mph. Measure your roller, if its the 45mm you can squeek a bit more out of it.

 

[MB Dave]

The roller is a 42mm.
Waiting for my Solex carby to arrive.
May try to convert one of the carbys into this. VeloSoleX S 3800 Carburettor
Although don't understand some of the terminology. eg. "dispersion jet"

 

[Mike B]

Got it mounted.

Need to get a smaller front tire, tire hits one of the motor bolts. Tire also hit the little plastic "archy" thing, so I ripped it off hoping I was done with tire hits. Nah, need a smaller tire.

Yeah, nothing fits right, typical China stuff -

 

[Adam F]

Finally got mine up and running! Rode 15 ks yesterday without a problem. Preparing to go for a ride today i rode up and down today and then "it" happened.
The clutch engaged and I was sitting still with the motor running at full rpm. For whatever stupid reason I hit the decomp lever killed the motor. Now I can't get the motor to start again! Any ideas on how to disengage?

I have tried riding up and down but it just wont engage!

 

[cannonball2]

Im a little confused is the clutch permantly disengaged? If so maybe the clutch or roller has come loose, The crank goes all the way through the roller to the clutch, which is in a drum attatched to the roller. They are held in place by retaining nuts maybe one loosened.

 

[Adam F]

Im a little confused is the clutch permantly disengaged? If so maybe the clutch or roller has come loose, The crank goes all the way through the roller to the clutch, which is in a drum attatched to the roller. They are held in place by retaining nuts maybe one loosened.

Sorry for the confusion. Yes the clutch is permanently disengaged. When I ride and release the compression valve nothing happens. The fan on the end does not rotate. I am thinking that it is because I switched the motor off with the clutch disengaged rather than a failure. Just can't figure out how to reengage the clutch.

 

[cannonball2]

The clutch is an auto clutch. Engine speed controls it. It locks to start, once at idle it disengages. It is engaged all the rest of the time. Something has to have come loose. The roller is probably spinning in its drum smoe how and not turning the engine, or maybe the clutch on the crankshaft.