BGF RB80, larger intake port?

I am looking into various HT kits, and noticed BGF is posting a different kit on eBay now. I had been looking at the Z80S kit, but I am seeing him posting up RB80, which looked identical.

I sent him a question about what the difference is, here is the response:

"RB80 is bigger intake port. 3 L tank, better parts. and runs smooth"

Maybe this is a 2012 change for all of the HT kits coming out of China? Any ideas?

I finally ordered my china girl yesterday (heehee), I did end up going with the BGF RB80 kit. There is not a single marking in the box or engine itself, so no idea what factory it came from, assumed it was a "Red Bat" because of the "RB" in the name?

Overall I was pleased with the "quality" of the engine. The castings are reasonably good compared to some of the others I have see on this site. There is still some cleanup to do, but overall not bad. I have not opened her up yet, though.



I did notice a good amount of metal shavings near the sprocket, though. Definitely going to have to give her a through going-through. Hopefully those shavings are not indicative of something trying to die before I even get started.



About the intake, the studs are 40mm apart. I noticed though that the intake manifold is aluminum, I think the others I have seen are steel? And it is also tapered, the inside diameter goes from 18mm round at the carb side to 20mm x 15mm rectangle on the motor side. And from the looks of the indentions on the gasket, the intake manifold pretty closely matches the intake port, woohoo. The port itself looks pretty clean, too.





I still have to pull the spark plug and move the piston to TDC to see how much of the intake port is covered by the piston skirt, that is a project for tonight.

On the exhaust side, there is a little slag where the port meets the piston, but not much. The exhaust itself needs a lot of help, though, to get port matched.

The front mounting studs are 40mm apart center to center.

biknut said:

That metal dust is probably from when they drilled the rear motor mount holes.

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I really hope so. I will feel better this weekend when I can dig farther in and see if things stay fairly clean or get uglier, lol.

The manual from BGF mentioned these motors were test run at the factory. I was thinking the oil residue I was seeing on the piston may have just been from assembly, but pulling the plug I can see it has definitely been run already. So either I got someone's refurb, or they really were test fired at the factory...

Looks like I need to do a little trimming on the piston skirt. I was hoping this would magically not be the case, lol.

Mannhouse51 said:

Keep us informed on how it runs please. Thanx

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Will do!

This weekend I took off the head and was glad I did, there were a couple small nicks on the squish band and one sizeable gash. I ended up sanding down almost half of the thickness of the squish band to get it out. After putting the head back on and manually turning over the motor by hand I did not hear the spark plug hitting the piston, so hopefully it was not too much.

Then when I tried to separate the cylinder from the crankcase, I could not get it to budge. After a few minutes, I chickened out and took it as a sign that I was not meant to be in there, lol. So the piston skirt will remain untrimmed until something goes boom and I have to rebuild, or I get to the point where I want to tune the crap out of this motor

Both the exhaust and intake ports look really clean as is, so now just waiting on my miscellaneous bits to arrive from SBP, trim the exhaust gasket and pipe a bit to more closely match the port, then install.

Al.Fisherman said:

Did you loosen these two bolts...It could cause the case to pinch the jug?????

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I did not loosen those, that might have helped, lol.

As far as the "larger" intake port, I think you are right biknut, looks like the difference is in the stud spacing. I do like that I do not have to modify the intake manifold to match the port, though.