What's Inside Your Grubee GT5?

I have rinsed a few engines out that burned through the piston crown,
When California switched to oxygenated gasoline, quite a few folks never re-jetted their carburetors to account for the extra oxygen in the combustion process. Result: waaay too lean.

Anyways, I digress.
Rinse the cases out by mounting it up in a jig that will hold it up-side-down.
I just used rope wrapped around the engine and hung them from a 2x4 laid across 2 sawhorses.
The method I used for making a sprayer was complicated and over thought. It also used an air compressor which I know alot of folks here may not have.
A much simpler method is to use a small diameter hose attached to lid of an old (well rinsed) dish soap bottle or whatever you can find that will hold a decent volume and be easily squeezed.
Stick the hose way up inside the cases at various places , hold the bottle up-side down, and squeeze it. Be sure to rinse every surface inside the cases very well and collect the rinse product in a tub or deep drip tray. Do not let it drain on the ground.
I re-use it over and over. If you store it in a paint can all the junk will settle to the bottom and you can skim off clean solvent from the top.
 
GearNut said:
I have rinsed a few engines out that burned through the piston crown,
When California switched to oxygenated gasoline, quite a few folks never re-jetted their carburetors to account for the extra oxygen in the combustion process. Result: waaay too lean.

Anyways, I digress.
Rinse the cases out by mounting it up in a jig that will hold it up-side-down.
I just used rope wrapped around the engine and hung them from a 2x4 laid across 2 sawhorses.
The method I used for making a sprayer was complicated and over thought. It also used an air compressor which I know alot of folks here may not have.
A much simpler method is to use a small diameter hose attached to lid of an old (well rinsed) dish soap bottle or whatever you can find that will hold a decent volume and be easily squeezed.
Stick the hose way up inside the cases at various places , hold the bottle up-side down, and squeeze it. Be sure to rinse every surface inside the cases very well and collect the rinse product in a tub or deep drip tray. Do not let it drain on the ground.
I re-use it over and over. If you store it in a paint can all the junk will settle to the bottom and you can skim off clean solvent from the top.
Click to expand...

Brilliant. So this is good enough to remove all the junk in there without having to crack it open, I assume. Thanks, Gearnut!!
 
I am not saying that it is a fool proof way to clean out the cases, I am just sharing a method that I have personally used.
When a piston burns through, most of the fried aluminum gets blown out the exhaust port.
Very little actually gets into the bottom end. What does get down there can typically be rinsed away.
When you have a mechanical failure and metal gets scraped and ground up, there is alot more fine debris that can work it's way into the nooks, crannies, and bearings.

Choose your method of cleaning carefully, dependent on what you are willing to take a gamble on if some debris remains afterwords.
 
GearNut said:
I am not saying that it is a fool proof way to clean out the cases, I am just sharing a method that I have personally used.
When a piston burns through, most of the fried aluminum gets blown out the exhaust port.
Very little actually gets into the bottom end. What does get down there can typically be rinsed away.
When you have a mechanical failure and metal gets scraped and ground up, there is alot more fine debris that can work it's way into the nooks, crannies, and bearings.

Choose your method of cleaning carefully, dependent on what you are willing to take a gamble on if some debris remains afterwords.
Click to expand...

Gotcha. I did rinse it out with your method, used an old water bottle and some extra fuel line, and it looks good for what I can see...there was some debris sticking along the magnet side of the case and I used a Qtip to get the majority of it and rinsed again. I also figured unless I tear it apart I am not going to get every last bit. I'm willing to gamble on it. I think...:)
 
I had a friend that the famous needle cage bearing fell apart on the piston. My thought was to put a new jug on it perhaps with a better wrist pin bearing. To take the bike to the car wash and flip the bike upside down. Then go crazy with the power washer. Last immediately flip the bike over and fill the crank case with simple kerosene gas [has a oil base to it] to prevent any rust, displacing any moisture and let that soak for awhile before draining it to stop all rust.

Then perhaps during assembly pour about 1 cup of oil in the crank case before start up
 
when i dissassemble a new motor, i use about half a can of carb cleaner, holding the case upside down over a trash can and spraying it inside, getting the little hose in every nook and cranny i can.

after i get the jug back on, i pour a capful of 2 stroke oil on top of the piston and work it up and down, being careful not to let it pour out the ports, so it runs down into the case, as well as lubing up the piston and rings.

as far as selling a new, re-worked motor goes, stay tuned. i've got some plans in the works...

i don't think there's hope for the "new, improved" CNS EPA carbs, though. the idle screw barely contacts the slide when screwed all the way in, the air mixture screw does almost nothing, the handlebar mounted choke lever blows. the cable isn't as long as the throttle, so it get's mounted near the stem, it only works if there's a ton of play in the cable, which also means you have to physically push the cable in to shut it off, and it's an ugly, cheap thumb shifter lever.

my personal opinion, is the new GT5's are crap. the fins are horrible, the 3-prong plug is garbage, the bicycle chain is weak, the clutch lever is lousy, the carb is useless, the cable housings are flexible rubber, the throttles are sticky, the intake manifold looks like the first project the shop teacher gave to beginning welders, a squirrel wouldn't even touch the acorn nuts, the pink air cleaner is, uh, feminine...

i will admit that it's packed pretty well, though. it comes in a nice box...
 
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bairdco said:
as far as selling a new, re-worked motor goes, stay tuned. i've got some plans in the works...
Click to expand...

Oooooo... I'd buy one. I'm not useless when it comes to mechanics, but I'd rather pay someone who knows what they are doing to do it for me. I'm more interested in cruising. Keep us posted!
 
Good thread... Tnx for the post! Inspired me to pull my basketcase apart a little to see what's going on inside it...
I'm making a bracket for a clutch cable roller like AL.Fisherman showed in one of his posts, and I went ahead and popped the clutch cover off... Good news, far as I can see. It was very clean inside, and barely a wear mark on the gears.
I'm going to let it be and not pull the clutch apart any further unless a problem develops on down the road.
rc
 

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Thanks for the great info, this will be my first engine. I am deciding between a jet, grubee skyhawk A raw and A flying horse, also the flying horse kit I am looking at supposedly has japenese bearings hi-perf carb, upgraded this and that, but may just be hype? you have a pref?

My main questions to you is this, what torque specs are you using to re-assemble, did you replace that head gasket, and what general tools are you using to clean these up?

Thanks very much.
.flg.



bairdco said:
I'm reversing some new Grubee GT5 motors, and found some nice metal surprises inside:
Click to expand...
 
i don't have a torque wrench, i just do it by hand. after years of wrenching on stuff, i have a pretty good feel for it. haven't snapped a stud yet...
 
If someone could write up a guide on the steps for prepping a motor for use, that would be astoundingly helpful.

I am a newbie and know nothing about engines, but would like mine to work as long as possible.
 
I don't think it's just Grubee, I think any of these Chinese motors need a good going over before you run 'em or you're asking for trouble....
If you have ever wondered why some motors live longer than others, its quality control stuff that wasn't up to par at the factory, if you run the motor right out of the box you're rolling the dice!
For instance, take this head on my Grubee GT-5 66cc. One of the four mounting holes was drilled slightly off center, this made the head mount a little off center and so there was only a small mating surface on one side of the head. I have to assume this head gasket was gonna blow on that side sooner than later...
 

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cirr.....
i'm up to about 40 builds for my customers now

the flying horse is advertised in several sites. they send you a skyhawk saying the are out of flying horsey....
i have stoppesd using ANY grubbee motors. all of my customers, none have gotten over 3500 miles on one. usually do to very low compression.

i switched to RAW motors. i've done 12 of them and NONE of them have come back for motor problems. some of them now have 10,000 or more miles on them. mine has over 7000 miles and stil runs strong.
however.......
they do not answer their phone, do not reply to left messages or email. i have heard of orders that have not been filld. i cannot confirm this though.
i wont order any untill i can talk with them.

my last 3 builds have been jets from pistonbikes and all of them are still going strong.
i dont do any pre-assmble, just install from the kit.

just my own 2 cents opinions
stay dry
gubba
 
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gubba said:
cirr.....
i'm up to about 40 builds for my customers now

the flying horse is advertised in several sites. they send you a skyhawk saying the are out of flying horsey....
i have stoppesd using ANY grubbee motors. all of my customers, none have gotten over 3500 miles on one. usually do to very low compression.

i switched to RAW motors. i've done 12 of them and NONE of them have come back for motor problems. some of them now have 10,000 or more miles on them. mine has over 7000 miles and stil runs strong.
however.......
they do not answer their phone, do not reply to left messages or email. i have heard of orders that have not been filld. i cannot confirm this though.
i wont order any untill i can talk with them.

my last 3 builds have been jets from pistonbikes and all of them are still going strong.
i dont do any pre-assmble, just install from the kit.

just my own 2 cents opinions
stay dry
gubba
Click to expand...

I guess you are out of luck then, cause raw motors is history, they sold out recently and are shipping out Grubee motors now. Don't know about the Jet motor, not sure who is importing them? The problem is the high fee's that need be paid to import these motors, most smaller companies can't swing it. So I wonder if there a big outfit out there with the cash to put on the line to import a fresh batch of Jet motors, or will they go away when the stock dwindles?
I have a couple Grubee's, can't really argue with you about the quality, they are kinda rough and do need some work straight out the box (not that I mind doing the work, when done they gotta be at least as good as any other china motor kit). That said, I would be willing to try another brand and see if I feel they are any better. Thanks for putting in the good word for the Jet motor, I may try them in the future if they are still available when I need one. Do you happen to know where they are manufactured and who is importing them?
Thanks again for your info...
 
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I don't know who made my 66cc engine/kit; I just put it on a old Huffy Mountain bike a few months ago and started riding it. To date, I have about 50 miles on it, so I'll keep my fingers crossed after reading on this forum. I picked up my engine kit in person in Kalamazoo, MI, at a motorcycle shop, here is the link Bike Motor Kits Motorized Bicycles Engine Bike kits The clerk offered to open the box and go through its contents for me; that was great, to be sure all of it was there and it was what I was looking for. There is no identification on this engine or its parts. I live about 150 miles from Kalamazoo, but it was near my route on a family trip. I think being able to at least look in the box for all parts and any damage, is a real advantage. Hoping to get many, many miles on this little gem and you guys too, regards, BMF dnut
 
interesting in Nightcruiser's pic that the head gasket, on the opposite side from that wonky hole, shows a marginal compression of the gasket... it is a thin line of compression, as opposed to the opposite where a wider bearing surface band shows.
...
the prob is, there is not really any cost effective fix for this QC boggle...

I guess the parts, new, are not all that expensive, but it's a shame something new will always be suspect if it is run.

I suppose I would run it, myself, but I would order replacement parts at the same time I was re-assembling it.

if I had the parts on hand I'd like to pull my own engine down and find out why compression is so low, and what the sharp clicking noise really is when I rock the engine back and forth with the rear wheel up on a stand...

Good luck
rc
 
rustycase said:
interesting in Nightcruiser's pic that the head gasket, on the opposite side from that wonky hole, shows a marginal compression of the gasket... it is a thin line of compression, as opposed to the opposite where a wider bearing surface band shows.
...
the prob is, there is not really any cost effective fix for this QC boggle...

I guess the parts, new, are not all that expensive, but it's a shame something new will always be suspect if it is run.

I suppose I would run it, myself, but I would order replacement parts at the same time I was re-assembling it.

if I had the parts on hand I'd like to pull my own engine down and find out why compression is so low, and what the sharp clicking noise really is when I rock the engine back and forth with the rear wheel up on a stand...

Good luck
rc
Click to expand...

Well, my first clue was when I had a hard time getting the wrench around this one head bolt, it wanted to interfere with the fins, while none of the other bolts did. I had thought it was probably a bad head bolt before I pulled it apart and saw what was going on. It was bound to fail since that bolt was harder to tighten AND there was less contact surface on that side of the head.
What I plan on doing is widening out the bad hole a bit in the proper direction and installing a new head gasket that hasn't been compressed unevenly. That should allow me to get the head mated to the cylinder on center. I thought about ordering another head, they're cheap, but then I figured the new one could be just as bad or worse, so I might as well correct this one and roll with it....
 
Yup.
I'd do the same thing.
Less than a minute with a rat tail file and you will have a better engine. lol
Simply marvelous QC, huh?
Good luck
rc
 
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