More Chinese junk, odd failure

[shenion]

A neighbor brought a small 4-wheeler over for me to look at ("Get MacGyver to fix it.")

It is a SUNL 90CC. Never heard of them, but are real cheap.

Figured it just needed battery and the carb cleaned. The carb was filled with green goo. Cleaned it out but all I could manage to do was have it backfire.

Turning by hand, I could hear the carb sucking/blowing as the crank rotated in any position. Figured it needed valve adjustment. The valve clearance still measured close.

On further inspection I found this:


No, that is not barrel distortion from the camera. The valve is bent. Odd is it sat 1/8" open and the clearance was still right on the camshaft. There was no "eyebrows" on the piston either.

So, the valve must have stretched as it bent. Must have bee a real soft spot in the metal.

Was about to tell neighbor it was trash, but decided to check on parts. An entire head with valves, cam, gear, springs, gaskets, covers, everything is $70 shipped. I can't even get a head gasket for one of my bikes for that price.

Dropped the new head in along with a new alternator stator. Looks like someone connected the batt backwards and fried the coils. That was $27; jeez. A stator for my GPz is something like $250.

Runs fine with new head but needs some more carb cleaning a sit does not idle well.

Even with slave labor, I can't see how they can make it so cheap even buying through a US dealer that has to mark them up.

 

[MrFluffy]

Ive seen that on two out of two of the chinese copy "honda" 90 kids quads Ive had my fingers in.
The last time I sent the owner off to buy a new valve for a 110cc variant, and a week later he got fed up of trying to find a distributer and just straightened it by eye rolling it between his fingers and giving it gentle taps.
It actually worked, despite all my dire predictions of the end of the valve falling off when it got warm, and a few months later he sold the quad on still running, it being too much for his 4 year old. Im pretty sure the material they use to make the valves isnt the correct grade, but *mostly* they get away with it. Never figured out what actually caused it on either of them though...

 

[dopplershift]

I think they can produce things so cheaply because its government funded, ****e conditions and they sell at a loss... only interested in receiving US dollars back... doesnt matter is they 'lost' money on the transaction... they'll just print some more.

 

[johnakay]

as for problems with carbs. soak the carb bits over night in vinegar
this should clear all the s**te out.

 

[Chipper]

A mate gave me a little ultrasonic cleaner, think it's an Aldi job, tenner or something. Haven't used it yet but he cleaned a bunch of carb parts in his, came out very nicely. Although there's something satisfying about fiddling with and cleaning carb partsby hand...

 

[shenion]

Were i used to work we had an ultrasonic cleaner. We used it to clean plotter pens. I'd love to have one.

I would not trust any acid for cleaning. My GPz carbs were destroyed by old gas that became acidic.

Turns out it was the plastic spacer for the carb was on the wrong way. Has an o-ring on one side and the carb has an o-ring. The two o-rings were facing each other.

 

[Pete.]

I cleaned out a set of carbs that has been left with unleaded in them for 7 years. The slides were stuck fast, even the floats were stuck on the hinges and the needles were stuck in the seats. Took me a wole (long) day to clean them up with carb cleaner and a jar of acetone. Would have killed for an ultrasonic cleaner back then I had to make do with tumbling the parts in a jam jar in my lathe. Did 7000 miles on that bike in 6 mths.

 

[shenion]

The carbs on the GPz i bought had old gas after it had ate through the petcock. Soaked them for 2 days in parts cleaner and nothing moved.

Finally got one of the sliders out and saw the jets had corroded so bad they blossomed up like a flower. They were beyond repair.

After seeing 4 sets of carbs go for $200+ on ebay, i found a set listed in the wrong category and got them for $40.

Old gas has got to have the nastiest smell that gets on you and lingers. The tank was beyond repair also.

 

[bucko]

my little bro had a cheep chinese make and the thing kept on brakeing all three of the bolts on the rear sproket sheard off at the same time once. needles to say we have yam's now

 

[Richie_asg1]

Chinese steel Hmmmmm.

You know all that scrap steel sitting on the scottish docksides - bits of burnt tyres and washing machines ? - well - we sell it to them, and they sell us machined parts

I worked in the Oil indusry making the reamers for drill pipe. We bought rough- machined reamers from China once. These 3 bladed tools are up to 20 ft long, with a core pipe of 14", and up to 48" diameter. That's about 2 - 3 tonnes of steel, and when machining them we spin them at about 200 RPM.

Now, that's normally ok, running on a steady band or on a cone centre, but you don't expect these things to crack lengthwise !

We lost 3 out of a batch of 6. Tbh - I don't hold out much hope for the other 3.

I don't think quality contol translates very well into chinese.

 

[bucko]

quality contol translates very well into chinese.

it dose its just something like "woww she'll do"

 

[shenion]

I did finish the 4-wheeler. Ended up having to run a #78 drill backwards through the idle jet (push out junk rather than drill it.)

New head is working fine. The neighbors kids are having a blast with them. Total cost for new head with valves, cam, cam gear, tappets, gaskets, springs (everything from head gasket up) with a new batt and alternator stator was $150.

Richie, I don't think most of the Chinese really do any QC on metals.

 

[bucko]

glad you got it running shenion

 

[Wallace]

Never figured out what actually caused it on either of them though...

Valve bounce by revving too high or the cam chain has jumped the sprocket. You don't tend to notice the chain having jumped a couple of teeth when you take it apart and then it's too late to tell anyway. Is the cam chain tensioner still manual on the Chinese engines?

I used to run early C90 inner valve springs on my 72cc SS50 so I could get past valve bounce!

Mike

 

[shenion]

Valve bounce would damage the seat. The seat was fine A slipped sprocket would bend the valve. Both would make the tappet clearance larger/smaller. it was still at spec.

The valve was 1/4" longer than it was supposed to be, so it stretched. Just crappy metal.

It did probably run lean, but I would expect an exhaust valve failure in that case.

 

[Wallace]

The valve was 1/4" longer than it was supposed to be, so it stretched. Just crappy metal.QUOTE]

I would presume the guide must have been acting as a stop against the bent section for the clearance to be there, was there any signs of the stem swaging? You would expect that if it was 1/4" longer! It must have been very hard to start and run really badly too.

Mike