Help me bring this ATV back to life!

[wevie]

Greetings and salutations!

I recently bought an abused non-running chinese ATV as a project for my 12 yr old to start learning on.  Previous owner said it ran before his buddy cobbled the wiring all up.  Cobbled is an understatement.  Just about every wire is cut.  But, these are simple motors so just getting it to run should be easy, right?


Ok, so there it is.

Here is a naked pic showing the motor a bit better.



The only thing I can find on the motor is Shenzen and 49cc.  I'm fairly certain it's a 1PE40QMB or similar as it has a 40mm piston.

We began without any spark.  After doing some troubleshooting it looked like just the CDI was shot.  We ordered a performance CDI and coil.  Installed and we have good spark!

Noticed right away that there was fuel leaking out of the head gasket so we ordered a new head gasket (and one head stud as one was broken) and I thought for sure we would have something now.

No luck.  Have spark.  Cylinder seems sealed well.  

Now, the oil injection doesn't work - to the best of my knowledge - so I just mixed some gas.  I even tried a spoonful down the spark plug hole but couldn't get so much as a pop out of it.

Now I'm thinking maybe it is a compression issue.  I can grab the flywheel (cover missing as you can see above) and turn it without any effort at all.  Not free spinning, but definitely doesn't seem to have compression.

We pulled the cylinder / jug and the piston looks pretty well worn.  

So now I come to you for advice.

1.)  Spark, compression, fuel.  That's all I need to get SOMETHING out of this.  What about spark timing?  Is it adjustable?  Can it be out of whack?  How do I verify this?

2.)  Visually inspecting the cylinder walls they seem OK.  No gouges or anything.  Should I just try ordering a piston/ring kit?

-or-

Big bore...  maybe just order a 47mm kit ?


Oh!  I just thought!!  Do these have reed valves?  Maybe someone buggered them all up.  I suppose I should check that out.

OK, so I only have weekends to play with this, so I won't be able to try anything during the week, but any advice you can give me to bring this back to life would be appreciated.

CRAP!  One more IMPORTANT question.  The electric starter motor is shot.  I've been just kick starting it.  This should be a reliable starting method, right?  Or am I going to NEED to buy a new starter?

[niz76]

Welcome!
Looks like you have a 1e40qmb Minarelli shortcase there!
I have brought many of these engines back to life! That's only a 50cc atv? You are correct in stating spark, fuel, and compression are the three main things needed... Do you have a compression tester?? 100 psi or so is about the minimum needed to get this 2t to fire. Sounds like you have spark and fuel. Most likely is low compression. You can eliminate the head gasket and use copper spray sealant or fuel resistant Ultra Grey to get more compression but if it's low from worn rings you'd probably be much happier with new rings or I would suggest a cheap 72cc (47mm) BBK... The reed valves and assy. are prone to air leaks which can cause you to pull you hair out in frustration so if you open it up be sure to clean and re-seal thoroughly (I like Moto1 Ultra Grey). Air leaks anywhere can bugger up your efforts so check head gasket, base gasket, exhaust gaskset very closely. If you do get it running don't let it run for more than a minute or two without those cooling shrouds in place!

Once you get the engine and carb dialed in correctly it will practically always start on first kick and you'll never miss e-start... it's nice to have the e-start while trying to get it started for the first time though!

[wevie]

What you see is what I have.  What cooling parts are missing?  I better get some if they are that important.

[90GTVert]

It should have a fan mounted to the flywheel, a shroud that goes over the fan and a shroud that goes over the cylinder. PFS , scrappydogscooters, and kaseaparts.com all carry them I believe or you can probably find that stuff on eBay.

As long as the key on the crankshaft that fits into the flywheel is there and not sheared off, most likely ign timing is alright. You can hook up a timing light at check if you'd like. Most run 13-16 degrees BTDC idling up to 2000RPM or so.

A compression test is the easy way to get an idea of what's up, but if it turns over very easily with the spark plug installed then most likely you have low compression.

If the cylinder and piston are in need of replacement, a big bore kit may not cost much more but should give you a nice boost in power. BBK will likely need carb tuning and possibly a roller weight change for best performance. You can find piston kits for about $25-30 IIRC at the same spots I mentioned for the fan/shrouds.

There is a reed block and valves under the intake. If they fail to seal or get damaged it usually causes a rich condition and flooding.

THe kick starter should work fine.

[stuckchuck]

Feb 22, 2015 8:14:40 GMT -5 wevie said:

What you see is what I have.  What cooling parts are missing?  I better get some if they are that important.

there are two plastic pieces that basicaly are two halves put together around the cylinder and head, one side has two bolts and a screw on the stator side to mount it, and the other side at the front of the case behind the belt cover is two rubber inserts that the engine cover and its little plastic pins pops into. look's like you'll need the fan as well, it mounts on the stator flywheel w/ 3 bolts






hope this helps there is all kinds of pics and info in the tech section

[stuckchuck]

A well lit pic of your spark plug, piston n cylinder walls and combustion chamber will help us determine the running condition it was in the last time it was alive.
As far as the piston goes, if it appears undamaged to the eye it might still be good and just re-ring it and hone it. Is there a black burn mark around piston below the rings? If so rings are shot and not sealing any more and letting compression and hot gases past them. A new 49cc top end will set you back about $50 +/-. If it was run with no shrouds by previous owner it is no doubt fried and should be look at a little closer. for the cost of a new top end i would go that route instead of just a ring n piston and a prayer. if you can't or don't get the piston and bore measured for clearence's your new piston n rings could be wasted in no time from a out of round cylinder.


check for bearing play in the crank when its apart and that it turns smooth w/ no hang-ups, drags, noise or clunk felt in your hand while rotating crank stub in hand. check that no movement in rod big end bearing some side to side is normal just no up n down

[stepthrutuner]

With one of the cyl. studs being broken suspect head warpage. Check it with a straight edge. Sand it flat w/180 then 320 paper on glass if needed or if the bb kit has new head there's your fix.

[wevie]

Feb 22, 2015 10:01:36 GMT -5 stuckchuck said:

A well lit pic of your spark plug, piston n cylinder walls and combustion chamber will help us determine the running condition it was in the last time it was alive.
As far as the piston goes, if it appears undamaged to the eye it might still be good and just re-ring it and hone it. Is there a black burn mark around piston below the rings? If so rings are shot and not sealing any more and letting compression and hot gases past them. A new 49cc top end will set you back about $50 +/-. If it was run with no shrouds by previous owner it is no doubt fried and should be look at a little closer. for the cost of a new top end i would go that route instead of just a ring n piston and a prayer. if you can't or don't get the piston and bore measured for clearence's your new piston n rings could be wasted in no time from a out of round cylinder.


check for bearing play in the crank when its apart and that it turns smooth w/ no hang-ups, drags, noise or clunk felt in your hand while rotating crank stub in hand. check that no movement in rod big end bearing some side to side is normal just no up n down

I'll have to see about pics.  Be next weekend before that happens.

Yes, the piston shows scorch below the rings.  Definitely feel that a full top end would be better than a piston and a prayer.

The head has some gouges where someone tried to pry it off.  Whatever kit I buy I would feel better with one that comes with a head.


Looking at parts-for-scooters a new top end is $90.  Is there a more affordable place?  The same price for a big bore from that vendor, but it doesn't appear to come with a head.

[stepthrutuner]

Brent knows most of the best and cheapest places to buy atv fare. Maybe he can clue you in.

[Corrosion]

Put it on TDC. And take another picture, It might have a sheared keyway, or mis installed flywheel. The raised portion on the flywheel is a trigger for the CDI. If you take a pic, at TDC. We might be able to see if it is close. By the raised section on the flywheel.

A compression test would be a good idea also.

[90GTVert]

If you're gonna buy a big bore kit then Parts For Scooters and Autotech355 are popular choices for sport/street style kits. I happen to have a Polini Sport on eBay ATM up for auction that no one seems to want. It's a good kit, has a 10mm wrist pin which is what I think the 50-70cc ATVs use. Scootertuning.Ca carries a bunch of higher end cylinders. The ATVs can use the same stuff as the scoots, at least the 50-70s should, just gotta make sure you get the right wrist pin size.

You can find some cheap 49cc stock top end kits on eBay, but some of them have little ports.

Don't forget the classifieds section of the forum.

[niz76]

Feb 22, 2015 18:36:56 GMT -5 90GTVert said:

If you're gonna buy a big bore kit then Parts For Scooters and Autotech355 are popular choices for sport/street style kits. I happen to have a Polini Sport on eBay ATM up for auction that no one seems to want. It's a good kit, has a 10mm wrist pin which is what I think the 50-70cc ATVs use. Scootertuning.Ca carries a bunch of higher end cylinders. The ATVs can use the same stuff as the scoots, at least the 50-70s should, just gotta make sure you get the right wrist pin size.

You can find some cheap 49cc stock top end kits on eBay, but some of them have little ports.

Don't forget the classifieds section of the forum.

I was considering buying that Polini kit right when u put it up for sale but I already have an Athena sitting on the shelf that I haven't found the right scooter for

[wevie]

Feb 22, 2015 18:36:56 GMT -5 90GTVert said:

If you're gonna buy a big bore kit then Parts For Scooters and Autotech355 are popular choices for sport/street style kits. I happen to have a Polini Sport on eBay ATM up for auction that no one seems to want. It's a good kit, has a 10mm wrist pin which is what I think the 50-70cc ATVs use. Scootertuning.Ca carries a bunch of higher end cylinders. The ATVs can use the same stuff as the scoots, at least the 50-70s should, just gotta make sure you get the right wrist pin size.

You can find some cheap 49cc stock top end kits on eBay, but some of them have little ports.

Don't forget the classifieds section of the forum.

I see both 10mm and 12mm wrist pin kits.  I'd have to measure the wrist pin I guess.  If you're interested in selling the kit outside of ebay (I don't use ebay) send me a message.

Searching for a 47mm kit WITH HEAD for around 90 bucks.  -OR- a stock 40mm kit WITH HEAD for around $50.

[stuckchuck]

most of the time the cheaper 47mm kit will cost the same as stock 40 mm kit or a little more. Most of the time a cheap stock bore kit wont have a head and is one of the things that cut the cost. Those can be found for 20 30 bucks if you need a new one. or search the classified section like brent mentioned or possibly post in the wanted section and someone probably has a good take off cylinder from doing a bbk just laying around...

I've bought a couple things from autotech350 and he's always been for me, right on the parts, cheap on the price, and fast shipper from the other side of the world! from the details in your first post i can tell you could handle a bbk swap,

the best option is a 47mm kit but unless you can tune a carb, read spark plugs, set up the cvt, have extra money to throw at it in other upgrades and tuning parts to maximize the potential or fix what that extra power wore out. a bbk can be a can of worms some people may not want to open.
For instance you can't just bolt on a new carb and "expect" it to be jetted right for your motor, because the ad says universal. So many things determine carb jetting like cc's of engine, port timing, compression, pipe timings or length, outside temp,and altitude plus many, many more all effect what jets each motor needs. it may be close enough to run ok, but melt a piston and start from scratch or worse take out the crank aswell and then cutting up a few spark plugs don't sound like such a bad idea after all

we're all here to help and no such thing as dumb questions.

[wevie]

Feb 22, 2015 20:10:39 GMT -5 stuckchuck said:

most of the time the cheaper 47mm kit will cost the same as stock 40 mm kit or a little more. Most of the time a cheap stock bore kit wont have a head and is one of the things that cut the cost. Those can be found for 20 30 bucks if you need a new one. or search the classified section like brent mentioned or possibly post in the wanted section and someone probably has a good take off cylinder from doing a bbk just laying around...

I've bought a couple things from autotech350 and he's always been for me, right on the parts, cheap on the price, and fast shipper from the other side of the world! from the details in your first post i can tell you could handle a bbk swap,

the best option is a 47mm kit but unless you can tune a carb, read spark plugs, set up the cvt, have extra money to throw at it in other upgrades and tuning parts to maximize the potential or fix what that extra power wore out. a bbk can be a can of worms some people may not want to open.
For instance you can't just bolt on a new carb and "expect" it to be jetted right for your motor, because the ad says universal. So many things determine carb jetting like cc's of engine, port timing, compression, pipe timings or length, outside temp,and altitude plus many, many more all effect what jets each motor needs. it may be close enough to run ok, but melt a piston and start from scratch or worse take out the crank aswell and then cutting up a few spark plugs don't sound like such a bad idea after all

we're all here to help and no such thing as dumb questions.

So far I find this a very welcoming forum!  I thank you all for your help and acceptance.

I guess I should take a minute and let y'all know that I do have the mechanical aptitude to tune one of these.  My background isn't in 2-strokes, but I've spent a bit of time around them.

Here's my ol' 2-wheeler.  


i.imgur.com/bqgHR9s.jpg

Usually, though, you can find me on four wheels either at the drag strip:


i.imgur.com/G7xjqrh.jpg

or more often than not, we are out in the woods or deep in a mud hole:


i.imgur.com/KPjqYdi.jpg

Now, I could just get my boy a new quad, but this is an opportunity for him to learn some mechanical skills.  Also to learn some patience.  Each time we reach a hurdle and have to order parts he knows it'll be another week!