BGF T80 total teardown

biknut · Oct 27, 2011

From now on I'm not taking any chances with crappy chinese quality control. I'm taking all my new china girl motors apart. This way I'll control the assembly process, and be able to inspect the quality of all the parts. But this thread is not going to be about putting anything together, but mainly about taking an average china girl motor from off the shelf so to speak, and dissecting it to try and find out what's wrong with it, if anything.

This new motor came out of a motor kit I bought on eBay, from BGF for $170 shipped. It was advertised as a T80. It's never been installed, and we're going to take it apart, and find out how good a job the factory did putting it together, and what do the parts look like?

The sticker on the engine says, The Rico Group inc.

biknut · Oct 27, 2011

Off with it's head. Humm, this combustion chamber looks pretty rough machined. Besides that, it doesn't look very high performance.

This is what I mean about the performance. The T80 head on the left has no squish band. The head on the right is from a X80A, also from The Rico Group. Notice the narrow squish band circling the outer edge of the combustion chamber. A squish band improves performance by allowing the piston dome to come in close contact to the squish band. Gas molecules close to the cylinder wall are squished to the center of the combustion chamber causing a more complete burn. This also reduces piston ping and allows higher compression.

biknut · Oct 27, 2011

Now the cylinder is off. The piston and rings look good. Better than any of my spares. The cylinder looks good with no flakes of nikasil coming off anywhere. I do think the acorn head nuts were bottomed out in the top of the nut. 2 of the cylinder studs weren't screwed in all the way. Both of those 2 studs are hard to thread the nut onto.

biknut · Oct 28, 2011

Now we're going to strip both sides of the cases and see what we find. The challange here is to lock the shafts to remove the fasteners. I going to put and penny between the primary gears to lock them, and remove the magnito bolt first. I was able to pull the rotor off the shaft by hand after that, which is normal me thinks. Then the drive sprocket comes off. I usually lock it with a spare piece of chain for some reason. It looks just fine after I get it off. Then you use the puller tool that comes with most of the kits to pull the pinion gear and the clutch hub off the transmission shaft.

After we strip the shafts I like to put a 2x4 against the transmission shaft on the sprocket side and whack it with a hammer to push the whole shaft assembly out of the right side. This one was tight so I heated it a little with a torch on the right side. The transmission shaft looks normal. The keys weren't to loose, or too tight. Basiclly nothing to report about the shaft assembly. It looks are good as the other one I have.

Now it's starting to look like a plucked chicken.

biknut · Oct 28, 2011

Take a look at this crank seal that was hiding behind the magnito. It looks like a leak waiting to happen. I'd give it less than 500 miles. It's always the details that kill it.

rustycase · Oct 28, 2011

Tnx Biknut,
I did not know the 2x4 method for driving out the drive shaft. I should have done that when I had my clutch off a few weeks ago.

Have you got the skf #'s for the bearings and seals?
They sure did a fine job slamming that one in !

How was the intake/exhaust match-up on the engine? and the gaskets?

I've got an un-fired redbat here that would have fed intake gasket to the cylinder in the first few miles... not much integrity in discount products.

Anyhow, great pics... enjoy the write-up!
rc

waistofhumanspace · Oct 28, 2011

Boygofast ripped me off on postage, luckyearlybird and boygofast are both Rico group = same twerps twice as many chances to sell crap on Ebay.

biknut · Oct 28, 2011

rustycase said:
Tnx Biknut,
I did not know the 2x4 method for driving out the drive shaft. I should have done that when I had my clutch off a few weeks ago.

Have you got the skf #'s for the bearings and seals?
They sure did a fine job slamming that one in !

How was the intake/exhaust match-up on the engine? and the gaskets?

I've got an un-fired redbat here that would have fed intake gasket to the cylinder in the first few miles... not much integrity in discount products.

Anyhow, great pics... enjoy the write-up!
rc

The bearings I found locally are made my NSK which is Japan. They better be good ones they cost $8 each. 6202VVC3

I didn't check the piston and port match. I'm just taking this motor apart. Whatever I build may not use any or all of these parts.

The intake gasket didn't match anywhere close. This motor has a big honkin rectangle intake port, but the gasket only had a little round hole. The exhaust gasket is a nice big thick rectangle shape, and still unused. Those kind seem harder to find. All the gaskets were installed with sealer. I haven't split the cases yet, but I don't like the looks of the center case gasket.

I'm thinking it will take about 4 motors to make one really good one, but I should be set up for spare parts after that lol.

biknut · Oct 28, 2011

waistofhumanspace said:
Boygofast ripped me off on postage, luckyearlybird and boygofast are both Rico group = same twerps twice as many chances to sell crap on Ebay.

I've had about the same experience on eBay as with the forum sponsors. My last motor was from LEB. It really was the biggest piece of crap, but no more so than what you might get from anybody else.

From now on I'm taking all my new motors apart and making sure they're built right.

chainmaker · Oct 28, 2011

Nice pics. Thanks for this thread

maintenancenazi · Oct 28, 2011

Thanks biknut for posting this! I'm in the same process myself with a BGF engine. It's nice to have that little extra peace of mind knowing everything is ship shape, BEFORE you fire it up for the first time. It's always good to avoid.... :-||

biknut · Oct 28, 2011

These pictures illustrate how tight a fit the crankshaft is in the cases. This wheels seem pretty close to center, but it's not just the side to side you have to worry about. I think the outer diameter of the flywheel touches the case.

biknut · Oct 28, 2011

I'm not exactly sure what to do about that. If I could I would probably turn the wheels down a little bit.

biknut · Oct 28, 2011

This is a tool I made to press the crank out of the cases.

maintenancenazi · Oct 28, 2011

^^^ Hmmm, would it be possible to just sand those areas on the case for clearance?

biknut · Oct 28, 2011

After checking this crankshaft for true, it looks like it might be the best one I've found out of 4.

One thing I notice about it that worries me are the big end bearings. They're the ones without the cage, just like the ones that failed in the last motor I had. There isn't an noticeable play in the rod though.

biknut · Oct 28, 2011

maintenancenazi said:
^^^ Hmmm, would it be possible to just sand those areas on the case for clearance?

I suppose that's the easiest thing to do. Eaiser than sanding the wheels anyway lol.

biknut · Oct 28, 2011

I'm hoping the bearing failure I experienced on the other crank was related to something other than the bearings not having a cage. Actually I would think the uncaged bearing would be better because it has more rollers. Harley cranks were built for years with individual rollers on the big end.

biknut · Oct 28, 2011

This is kind of nit picky but it's a slight concern for me. The case on the right is the new T80. On the left is a case from a X80A. This is a close up of the rear motor mount holes. The T80 is drilled a little too close to the edge of the casting for my liking. I'll probably ignore it, but I'm on record now saying it could cause trouble. This is just one of the hundreds of ways one china girl motor can fail while another identical one is fine.

biknut · Oct 28, 2011

That's about it for this tear down. The only last thing I'll do is remove the crank bearings from the case. Since I won't be using the stock china bearings I'll just heat the case a little and whack the bearings out with a hammer and appropriate size socket. I'm not planning to disassemble the crank assembly, because I don't have the proper tools.

This motor was imo only average. The crank seal on the mag side would have caused problems in a short time. The motor mount hole in the case isn't great, but if the motor is installed well it probably will survive. The head casting is rough, and low tech, but it would get the job done. The screw holding the pinion gear on the crankshaft was not very tight out of the box, but this is the kind of thing you should check before start up.

I'll be glad to answer any other questions you might have about this tear down.

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