So I got a GT80 from GB. It came with a flex exhaust. The poo poo pipe is way to restrictive. I took my Dremel tool to the exhaust to open that up a lot more than it was stock. I plan on getting a different pipe for this bike soon. But I am using the flex exhaust for now. The next thing I proceeded to do was take this engine apart and correct all the Chinese crappie worksmenship. I'm going to include pictures of most of the things I did to the motor. Yes I did find metal shavings inside of this motor. Yes they're porting was crappy. As with any of these two-stroke kits you have to take them apart to make sure they're put back together how you want them. I ended up correcting the top sides of the transfer ports. As well as opened up the transfer ports on the crankcase. I also put a proper hole in the intake side of the piston to help the Reed valve work better. They put a boost port on the cylinder from the factory. You know the Reed valve the Boost port the three piece clamp sprocket and the exhaust Plus the cylinder head we're all reasons I bought this motor. I'm going to try to include as many pictures as I can of what I did. This way anybody else can see what you gotta do to get these motors up to Snuff. I probably put a good 10 hours of porting into this motor I finally got it together and have only wrote about two miles and so far the CNS Carburetor is giving me fits. But then again I haven't had a chance to take it for a proper Drive. I'm running opti2 at roughly 70:1 for break in.
GT80 in a Schwinn Swindler Project Tight Squeeze
- Thread starter Neptunati
- Start date
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- Tags
- gt80 reed valve
Bike as it sits now the reason I call it project tight squeeze. I had to sand down the back of the head also had to sand down the spark plug boot that engines barely fits in there. Also the rear engine mount was basically cut in half and then sanded it down further. And the front engine mounts had to be angled and ground down to fit this engine in. anymore and I don't think I could have got it to fit without being welded in with even more special brackets.
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mike carter 2
Member
i also put a gt 80 kit in my bike.i only spent a little time port matching the intake and exaust.made 1979rm 60 x chamber fit,ported the piston,and sanded a little bit off head.i ride it daily ,and run it pretty hard at times...no trouble at all.i pt the kit into a shwinn blackwell frame.all kinds of room,welded in motor mounts.bike handles great due to larger tires.thers a pic in the high proformance thread
mike carter 2
Member
allmost forgot ....JUNK THAT FLEX EXAUST!!!!!!!!!!! its to restrictive
Yeah I want to get rid of the asap. You got any pics of your pipe? Did you also put a hole in your piston? What do you mean you ported your piston? I took out the stupid spacer in the intake. Yeah these motors look almost exactly like the arrow motor. It's pretty much a complete rip-off it seems like I discovered that after I bought it. The Reed valve box looks exactly like theirs. I'm pretty sure it's all reverse engineered from an arrow motor. And the head is a rip-off of the Fred head as well looks exactly like it. I just wish I had a fred head to do a side-by-side comparison. Not a bad deal though for 300 bucks
mike carter 2
Member
check out reed valve engines on the high proform profromance part of the foram. the only way to make useable power from a reed valve motor is to use a ported piston .and yes i drilled a hole in my piston, then took a dremmel and made a hole about 1 1/2 around ,i dont think it large enough
I got it to fit.. And all I did was to grind the front mount bolts down a bit, inabling them to fit around the bikes tube on its frame.
It may have weakened the strength, but I used good steel ones not China steel witch I did try grinding too.. A lot easier buy the way. Then using loc tight it worked great.
It may have weakened the strength, but I used good steel ones not China steel witch I did try grinding too.. A lot easier buy the way. Then using loc tight it worked great.
Tyler6357
Well-Known Member
You were smart to take it apart and fix the porting. Just 2 things, (1) I would replace that spark plug boot with a quality rubber one from the auto parts store, those stock plastic ones that require you to remove the cap suck! (2) seems like a pretty long header on the pipe, are you out of the power band at wide open throttle? You could cut a few inches off of it but it might be better to get a larger chamber.
Yes I'm definitely looking to getting an expansion chamber. This motor feels like it has so much more but it's just being so restricted by the exhaust. I opened up the exhaust tube Inlet as much as I could with a Dremel tool but it is freaking tiny. That pipe gives this bike all sorts of torque gobs of torque. It climbs Hills awesomely but it tops out between 33 and 35. And I do need to get a smaller shorter spark plug hopefully they make one that's hot but short physically. The Fred head ripped off that gas bike back engineered from him is super thick and you need a hot spark plug to get the electrode all the way down in the chamber. But you can see how tight it is in there I mean the spark plug boot is all the way up against the frame I can't even get the spark plug out unless I unbolt the engine and rotated out a little bit. It freakin sucks. I had to sand down the front side of the head in the spark plug boot itself to fit the engine in this Frame. But I love this bike and it feels great at 35 miles an hour. This Springer Fork on there is actually functional really good. Regular forks go up and down this one kind of Dives forward so even though it has all that travel that you need it doesn't feel like it when it physically does. Well I stay in the correct myself here you only have about maybe 2 or 3 inches of travel on the Springer Fork but it handles potholes and bumps really really well. I just like the drive feel of it compared to like mountain bike Forks which I've had an old motorized Diamondback in 08-09was my first build. I'm definitely going to get a proper dirt bike expansion chamber and put it on here. Then this damn thing is really going to fly. I got the 27 and a half inch Tires Plus a 40 tooth sprocket. Anybody know what RPM's would be say it 50 miles an hour?
Tyler6357
Well-Known Member
Hey, I understand the problem in getting it to fit but those boots are known to fail. I know because mine started to arc when the wires vibrated loose and melted the plastic all over the plug and the head. I know that the good boots don't require you to remove the spark plug cap but that doesn't make it much taller. The rubber ones might actually be shorter and fit better because they are rubber and will have more give than the plastic ones, you can probably get a short one from the auto parts store. You can see how far mine sticks up.--> http://motorbicycling.com/album.php?albumid=1062&pictureid=11021
Yep definitely going to replace the boot I'm already looking at alternate boots. But I'm on a tight budget so I have to see what I can do trying to Source local LOL around my garage but I can't find anything. I'm looking to get a short spark plug with long threading. Just like the other spark plug I had in there or it's just enough so that it is in LOL the combustion chamber but no threads showing I'm wondering if they make one?
Tyler6357
Well-Known Member
I'm not sure how short they make the spark plugs but the boot I got only cost $5 at my local auto parts store.
I think if you changed out that front mount and laid down on the case you would get more room for the spark plug wire. I agree that exhaust pipe is too long. I was wondering if you put the piston port in or did come that way?
I have the same problem with clearance on my bikes. they are such a compact package it's hard to fit it all in there.
I have the same problem with clearance on my bikes. they are such a compact package it's hard to fit it all in there.
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What are you saying "lay down on the case"? The front mount is the same one that came with the kit. It's a U bolt with a zigzag type plate. The other side of the U bolt has a half circle plate that goes in between the U bolt and zigzag plate that attaches to the engine. I had to grind the rear inner part of the half circle plate way down and bend the zigzag plate to match. So the whole front mount is staggered to squeeze the engine in. I hope you can understand my explanation. Here's a picture of the front mount. You can see the plate that's in between the u bolt and the zig zag plate that attaches to the engine. And you can pretty much see how its staggered and how its kind of leaning backwards towards the engine. There's no way to get a picture of the inner side of that plate without taking it off the bike. That's why I named This Thread project tight squeeze LOL. Also the tip of the cylinder head that's touching the steel bar from the bike I had to grind that down so when I angle the engine and it would be able to slide in there. The exact to Middle fins on the cylinder head are actually touching the crossbar there on the top. I didn't want it like that but it actually works out pretty good. The front engine mount on the physical engine is too small to fit my bike tube unless I somehow I grinded it bigger but even if I did that the holes that are tapped for the bolts for that amount wouldn't fit at all. I didn't want to cut the bike anywhere so that's what I had to do. Your bike in the picture there is that custom made? That's a pretty sweet looking bike I really really like it. You know that cylinder head that comes with the gt80 kit is a reverse engineered Fred head. I think Karma would dictate the next bike I build I actually need to buy genuine Ford parts. Because gas bike totally ripped him off. I don't think they sell that head on its own it only comes on the gt80 kit all the other heads that have listed on their website are different. It's a great head I tried it on a different bike with a 66cc motor and the difference was night and day. The only thing is the things are extremely sharp you can cut yourself really easy they didn't give her anything on the top of the head I really love the gt80 kit. I've got maybe 50 miles on the bike now and the Reed valves are just awesome for torque. But like I've been saying that stupid Flex exhaust is so restrictive where it meets the engine it actually is even slimmer it's maybe like point 6 inches and the inner diameter is maybe even a half-inch it's tiny.
And you're talking about the hole in the Piston? No I did it myself with a Dremel tool and you can see how rough the edges are sending them down I was kind of thinking about taking it back out and making it even bigger but I don't want to screw up the good thing I've already got going. I cleaned up the inside of the transfers and kind of ground in a little bit bigger and then matched to The Jug and opened up the transfers on the case really big as you can see in the pictures. But no there is the third transfer Port that they put in The Jug but the piston I had to make the whole myself. Why they didn't do it from the get-go I don't understand. I never ran it without the hole in the Piston so I don't know what it ran like before but this thing runs extremely well **** I got it set up. I probably got like 10 hours of Dremel work in that motor. I got it setup to go buy a CR85 Honda expansion chamber on payday. I just need to find a welder in my area to set it up for me. I basically wanted to look like Vince's bike how he has his exhaust setup
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I didn't realize the bottom tube was bigger than the case. I was asking about the piston port because it looks awful big to me. I put one in my case inducted motor when I showed it to my friend that builds jet skis he said mine was to big for such small motor. Mine seems to work real well. at 5000 ft. it goes about 35mph but when I take somewhere with lower elevation it get to about 45mph. If you look up " Going case inducted" on this web sight you see how I built the motor. it runs real strong. I'm working my fourth BTR and building another case inducted motor. I'm glade you liked my bike. I just love working them.
bluck
Active Member
What bike is that?! Looks awesome might want to have one, one of these days
I make the frames from used bikes I get changing the seat post to go back instead of up. I also build all my own motors. I now have four of these bikes.