Bad engine?

marioaz · May 31, 2009

I have two Grubee GT-4 kits. Kit #1 on an old DiamondBack. Kit #2 on a Point Beach. #1 has about 800 miles on it, other than typical gear whine it always sounded tight. Plenty of power, especially after break-in. Nice powerful popping exhaust note.
#2 right from initial start up rattles so bad from the cylinder area that it sounds like it's getting ready to throw parts. It now has about 300 miles on it and hasn't developed any more power. It's gutless and slows way down on hills that #1 takes easily. The exhaust note is also quieter. Starts right up, idles, accelerates smooth from stop. The plug looks good and I've tried different plugs gaps with no change. I'm guessing the whole top end is junk.
Both bikes have new plug wires, NGK caps, B6HS plugs.
The vendor for #2 has already had to send a new clutch, and clutch lever.
Did I just get a lemon?

Spunout · May 31, 2009

like my pal azvinnie says, "it's a crapshoot with these motors." thats the best way it can be put, imho.

ive been riding bikes for 5 years. my first two motors had 15,000 and 12,000 miles before giving up the ghost. the last motor i got lasted around 700miles and i havent tore it apart yet to find out why, but it wont run and makes some grinding sounds.

a vendor told me that and average of 1 out of 100 motors are lemons.

no quality control. gone are the days, when the chinese held their pride in craftsmanship up for the world to admire.

they've become westernized, and now its all about $$$$.

Bikeguy Joe · May 31, 2009

I couldn't have said it better Spun!

These engines are like buying a pig in a poke.
For you young ones out there, or city folk, that means "Buying a baby pig in a tied sack".

You just never know what you are getting.

Retmachinist · May 31, 2009

I totally agree, you just never know what you are going to get. I have now purchased six kits from six different vendors. I am very happy with four of them. The other two, one runs fine but sounds terrible, like it is going to fly apart at any moment. The other one sounds o.k. but is just a complete dog! It just won't open up and has no power going up a hill. I have tried every tune up modification mentioned on this blog, and I am convinced it is just a Lemon!

John

marioaz · May 31, 2009

I think it's time to tear it down and install new top end. I don't feel like hassling the vendor. Maybe I can get a discount on the parts. It seems that the kits are simply guaranteed to run, not fly apart, but not necessarily run well. Both kits were apparently "bench tested". Can't they reject an engine that sounds like marbles in a can? There may be so much noise in the "shop", that even if they wanted to, they couldn't hear a bad one. I would gladly pay more for increased quality control. For the next engine order I'm going to demand a verbal that if it has excessive rattle, no power, or whatever, it's being returned. If enough of us do that it may get results. I can understand the disapointment when a first build is a lemon. Anyone have a Creative Engineering motor yet?

spad4me · May 31, 2009

You need to find a good dealer.

For example I use an sk 50 rc engine and love them.
But I will only buy then from kangakee USA. and around the seams ATS hobbies
They test thousands of Chinese S K engines to sell me one .
No kidding at all thousands to get one good one.
Many people have bought straight from the factory only to discover they have only saved three dollars and bought trash.
The Chinese have NEVER had any Quality control.
They do have craftsmen and artists.
But not in a factory.

deacon · May 31, 2009

I differ from the chinese ever holding their work up for the world to see. I bought cameras from them 15 years ago and they were horrible. They were assembled with slave labor from political prisoners. I have had them come in with screws missing that made them leak light or totally useless without black tape. That 'patch them together' mentality is a lot like now.

Cabinfever1977 · May 31, 2009

your gt-4 kits probally were not cheap and should have a waranty and they should run good with there improvemnets over last models. i would contact the vender.
i have a gt-2 from gasbike and mines running great.

chrisme · May 31, 2009

Have you tried switching the carbs around? The second kit could just have a bad carb.

reg454 · May 31, 2009

I thought my engine was blow a little while ago when it dies and would not start. What was wrong with it was the inner clutch spring was too loose, I tightened it up all the way I could then readjusted the flower nut and bammm started and ready to go.

The mods i have done to the motor are I removed the bottom gasket from the cylinder and filled both side with a file to make them smooth/ rtv sealant to make it airtight. shorted header length by 1", removed the clutch plate and used a 2" die grinder to make the area flat and uniform pattern for grip. Run great!!! I need to get or make a custom exhaust to make it quieter, Also duel pull brake lever and use then other long brake lever as my cluth handel works alot better than stock.

marioaz · Jun 1, 2009

In the morning I'm going to switch carbs first, then muffler. If that doesn't work I'll contact the vendor. They've been great so far. So, #2 when under load uphill starts pulling and then comes out of that mode and just runs smooth and doesn't have power and can barely make it. It wants to pull under load, but just for a moment. #1 will go into that pull mode and stay there right up a hill.
To end the evening, I removed #2 muffler and end cap and the upper flat plate that the end cap long pipe goes through is not attached to anything. Screwed the end cap back on and shook it and things are loose and rattling in there. Thumped on #1 muffler still attached to bike and no rattling. This is getting interesting.

fm2200 · Jun 1, 2009

It sounds like it could be a problem with the reed valves, if there not installed properly or left over shavings are fouling there function. If they not seated correctly poor performance is a sure thing. The reeds are the valves of a 2 stroke.

Bikeguy Joe · Jun 1, 2009

GT4's have reeds?

floridaboy · Jun 1, 2009

Well it seams like i am in the same boat. I bought two Gen II engines and you would think they were two entirely different engines. They are easy to start and seam to sound the same when running but one engine pulls alot harder then the other. When i checked the carbs on one engine the one that pulls the best the needle is in the center groove and the other one is in the top groove. I tryed to set the weak engine carb to the center groove but it made things worse. It could be the carbs I should have switched them but i no longer have the second engine it is in St Augustine now. That is the good one.

Bikeguy Joe · Jun 1, 2009

Grubee Gen II's aren't any different than any other chinese engine....meaning a crap shoot in quality and performance. One could very well out perform the other.
Also see- "pig in a poke", and- "chinese quality control = oxymoron".

Cabinfever1977 · Jun 1, 2009

i dont think they have reed valves. they have new no-intake carbs and some other stuff like a inline clutch cable adjuster, larger engine bearings,stronger bottom end,steel piston sleeves,slant head with slant plug or something,and engine mounts and tensioner for larger frame bikes and some other minor stuff.

marioaz · Jun 1, 2009

Here's where it is so far. All the rattling is not from the cylinder area/wrist pin, etc. It's the muffler innards rattling. Bad muffler?
Ran the bike without the muffler end cap and air filter. Pulls just fine now. way faster. Does have some cutting in and out WOT, at 25mph or so.

chrisme · Jun 1, 2009

marioaz said:
Here's where it is so far. All the rattling is not from the cylinder area/wrist pin, etc. It's the muffler innards rattling. Bad muffler?
Ran the bike without the muffler end cap and air filter. Pulls just fine now. way faster. Does have some cutting in and out WOT, at 25mph or so.

I have the black muffler, and it is insanely restrictive. Taking off the end cap gives it much more power. But it sounds like an angry chain saw...
This is what I did... I took of the end cap, and bent part of the rim in a bit. So it doesn't make a perfect seal with the big muffler tube. This allows some exhaust to get by the end cap, but most of still comes out the end pipe. Don't need to do it much, and you get the same power as without the end cap. But you have more back pressure, and it is quieter. Win-win

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Bad engine?

marioaz

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Spunout

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Bikeguy Joe

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Retmachinist

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marioaz

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spad4me

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deacon

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reg454

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Bikeguy Joe

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