Skyteam GT200 - Loncin engine.

[alchemysa]

(My first post asked about the timing chain tensioner but perhaps some general info about this bike may be of interest to some members.).

I recently bought this bike for $600 on Gumtree. (Thats a bit like Craigs list). I don't know how that price rates in the U.S. but I think that was a reasonably good price here in Australia. Its a Skyteam dirt bike with 200cc OHC Loncin engine. Best thing about it is that its electric start! Its not a common bike over here. Chinese bikes are still pretty rare I think. The bike had plenty of war wounds but I dont think its actually done a whole lot of running. I'm told that Loncin engines are relatively well made but I haven't had it long enough to confirm that.

Since getting the bike heres a few things I've done to it.

• Got it running. It had a faulty spark plug and a faulty spark plug connector. Both faults caused intermittent spark failure and occasional total shut down. I suspect the previous owner had lots of problems because he couldn't diagnose this correctly. This is the second instance I've encountered in just a couple of months where spark plugs have appeared to be OK when earthed but were actually failing when under load.

• Added a key and a neutral indicator light. (The bike had no key. Anyone could start it with the press of a button. Fortunately there was wiring I could tap into to include a key and a neutral light which is pretty much essential in my opinion.)

• Cut 2" from the front fork springs. This lowered the bike about 1.5". I also wound the rear shocker to its lowest position. I'm only 5'8" and this bike felt very high. I ride in sand a lot and like to sit reasonably low. I might even drop it a bit more later on.

• Cut and reworked the airbox so that it lines up correctly with the carby. (Distance from airbox to carby is only about 1 inch so if it doesn't line up correctly its a real pain to install the carby. Much of the 're-sculpturing' was done with a soldering iron as described below.)

• Repaired lots of broken and cracked plastic. Repairing plastic body parts is a skill thats very easy to learn, very satisfying, and a real money saver. All you need is a cheap soldering iron and a hot glue gun. You can find the technique explained on Youtube but basically all you do is hold the broken parts together and melt them together on the backside with the soldering iron. I use a kind of deep 'cross stitch' pattern on the back for strength and a smooth continuous gliding action across the front to seal the crack. The Hot Glue is an additional innovation of my own. On the backside of the join, where it won't be seen, I cover the 'soldered' joint with a 1/2 wide path of hot glue. This stuff is very strong but slightly flexible so it adds a great deal of durability to the join. Hot glue guns are only a few dollars each and the glue sticks are only a couple of dollars for 12. This simple combination of soldering iron and hot glue gun will return the plastic panel or mudguard to original strength and can also be used to reinforce plastic parts that may be prone to cracking in future. If necessary the hot glue can also be neatened up or shaped with the soldering iron or a stanley knife blade. You could go even further and repaint the whole panel to return it to as new appearance if you wish but I don't mind the look of a few battle scars.

I've managed to collect a few useful parts diagrams, an operators manual, and a few other bits and pieces for this bike so if anyone wants anything, sing out.

Cheers.

[katoranger]

Looks nice. I think you did fair on the price.

[SpudRider]

Welcome! That is a nice looking motorcycle. The UM dirt bikes had a good reputation in the United States.

[MICRider]

That is a good looking dirt bike! I like the thermal wrap on the header pipe vs a rattly heat shield .

I've never heard of that plastic repair method, I'm going to have to look into it!

[alchemysa]

Originally Posted by MICRider

That is a good looking dirt bike! I like the thermal wrap on the header pipe vs a rattly heat shield .

I've never heard of that plastic repair method, I'm going to have to look into it!

Plastic repairing is kind of addictive once you've learned how to do it. I'll post some close-up pics later today.

The thermal wrap was on the bike when I got it. I'd planned to make or buy a heat guard but I might leave it on. It still gets pretty hot but its better than bare metal. Important thing is to make sure its dry when the bike is put away or it will promote rust.

That reminds me that another repair that I forgot to mention was the muffler. I drilled out some rivets and took it apart and found it was broken inside. I can't weld stainless so I fixed it with some brackets and large pop rivets. I stuffed it with fibre insulation and pop rivetted it all back together. Good as new, and quiet now.

[Weldangrind]

Good tip on the glue gun. I've done plenty of plastic welding before, but I've never thought of reinforcing it with hot glue.

[alchemysa]

Originally Posted by Weldangrind

Good tip on the glue gun. I've done plenty of plastic welding before, but I've never thought of reinforcing it with hot glue.

The hot glue hardens to about the same consistency as the base plastic. Not too hard and brittle, but not too flexible either. I think it provides some really useful strength to the repair.

I use it for lots of things. I like the fact that you don't have to wait for it to dry. I recently patched the rear bagger on my ride-on mower. I used some shadecloth to cover the tear, glued it all together with some hot glue and sprayed it with some black paint. It looks neat and its probably stronger that ever.

I also used it to repair a crack in the plastic wheel flare of my Pajero 4WD. Even without any 'welding' its still holding together after about 2 years. Surprisingly, spray paint seems to stick to it pretty well if you rough it up slightly.

[SpudRider]

How did you add the neutral indicator light?

[alchemysa]

Originally Posted by SpudRider

How did you add the neutral indicator light?

(My memory is a little fuzzy on this and I've just had a couple of beers, so i might have a few details wrong.).

There are about 7 wires coming from the gearbox. These wires go to a connecter under the fuel tank. On the street version of this model, with a full instrument cluster, these wires go to a neutral light plus 5 LED's indicating each of the gears. I had none of those luxuries, not even a key, but I do have electric start so the neutral light wire (light green and red in my case) instead goes to the safety shutoff switch and starter motor relay, so the starter motor won't work unless its in neutral.

(So if you have an electric starter, or some other thing that prevents it from starting 'in gear' you'll probably have a neutral wire somewhere).

I cut the green/red wire at the connector, put a 12v light and a key in series, then completed the circuit back to the wire I had previously cut.

(Correction. Only the key is in series. The light is connected to the key but takes positive from a red wire somewhere.)

One blunder I made was that the key doesn't actually switch the engine off. It just completes the neutral light / starter motor circuit. I still have to use the safety switch to kill the motor, and the bike can still be kick started even when the key is removed. But I'm not worried about that. Its enough to confuse people and its a bit of a pig to kick start anyway. The main thing is it now cant be electrically started without the key. But the real reason I had to add a key or switch to the circuit was that without it the neutral light would ALWAYS have been on when the bike was in neutral, even when not running.

Now I'm getting really fuzzy ... The neutral wire and 5 of those other wires from the gearbox are basically just continuations of the negative circuit. The 7th wire is the negative 'in' wire. So you can easily identify which is which by tapping into them at the connector then running to the positive pole of the battery, (with a 12v light in between of course.)

Theres probably a few different ways to add a neutral light circuit. The basic thing to remember is that the neutral wire from the gearbox is a negative wire not a positive wire. Youve just got to tap into it, add a light, then complete the circuit to a positive wire somewhere.

By the way, my old 84' Honda CT 125 only has kick start but it does have a factory fitted neutral light. In this case it only has one or two wires coming from the gearbox. I think it would be pretty rare for a reasonably modern engine not to have a neutral sensor of some sort even if it doesn't have a light.

I hope thats some help and not too confusing. Are you thinking about this for a bike with electric start or some other type of neutral sensor?

[SpudRider]

Thank you for taking the time to write such a detailed explanation. My Honda XR650L and Zongshen 200GY-2 (Yamaha clone) each have neutral sending units exiting the left crankcase cover. I didn't realize the UM dirt bikes had a wire coming from inside the engine which provides the signal when the gearbox is in neutral.

[alchemysa]

Originally Posted by SpudRider

I didn't realize the UM dirt bikes had a wire coming from inside the engine which provides the signal when the gearbox is in neutral.

Spudrider, I'm new to chinese bikes so the UM/Skyteam link is a bit of a puzzle to me.

My Skyteam dirt bike (GT200 or ST200) has a Loncin overhead cam engine. I was lucky enough to find an operators manual for the street version of this bike. Fortunately it had a wiring diagram. My overall wiring is much simpler but the basic parts of the loom are common including the 7 wires from the crankcase, one of which I tapped into. 'Skyteam' was/is a name used in Australia and Canada and a few other countries.

The UM situation is somewhat confusing. I have a parts catalogue for the 2006 UM bikes (SMF, DTF and DSF 200) but they clearly show they are pushrod engines (with a neutral sensor in the crankcase by the way). They must have changed to OHC engines later on because Skyteam Canada is still in business and says their OHC parts are interchangeable with UM parts.

Skyteam is still making bikes in China but UM seems to be gone. Were they just Skyteam bikes rebranded for a US outlet called UM?

[SpudRider]

United Motors (UM) sold bikes in the United States; they went out of business a few years ago. They sold rebadged, Hyosung street bikes manufactured in Korea. They also sold rebadged, Zongshen dirt bikes.