Hi all.

I've been scouring the net for the last couple of weeks trying to get as much info as I can on my own. I hate asking questions if I haven't at least tried to find the answer on my own. It's getting exhausting so I've decided to swallow my pride and start asking..

I tend to give too many details when I ask questions, but it makes it easier for people to answer if they have all the info...so here it comes.

I purchased a SMC Urban 50 from a local junkyard for about $85. It took me about a week to actually figure out what type of ATV it was and then a couple more weeks to find out more info on the engine. SMC (Standard Motor Company) is apparently a German based company who has set up camp (manufacturing facilities) in Taiwan. The engine is, as I have been told, a minarelli 1PE40QMB clone. There are no stamps or markings on the engine to confirm this, which is why it took me so long to figure it out.

I was told at the time I purchased it that the engine was not running. I noticed some aftermarket parts on it and figured I could part it out and make my money back if I couldn't fix it. This is what it looked like when purchased:





Now, before I start getting into details, please understand that I AM a mechanic ('certified' while I was in the Marine Corps). I rebuilt my first car engine at 15 and haven't turned back since then. I'm now 44 years old and there has never been a time in my life when fixing/upgrading/general 'fiddling with' cars has NOT been an almost daily task (joy). That being said...the last time I dealt with a 2 stroke engine was literally an 'Introduction to Combustion Engines' class my first year in high school which was centered around the basics of a briggs & stratton lawn mower engine...which is to say pretty much NEVER.

Well, I took it home and opened it up....it was a mechanics NIGHTMARE and something that most people would probably just cut their losses and toss away. But, I'm kind of a hard head and didn't want to give up on it. 'It' being a seized starter motor (rust), rust on the stator points (points?? is that the correct term?) and some nastiness in the variator/clutch housing that would scare most people away:



After a bit of cleaning, brushing, scraping and what-not, I was left with this:



I then cleaned out the gas tank (looked as if pure oil had been poured into it), cleaned out the carb, replaced the spark plug and battery and it started up without a problem (much to my surprise!).

I took it for a ride up and down the street and everything seemed to be working fine. I was quite pleased with myself. I took the paperwork down the the city office and registered it (I'm in Japan, that's the way things work here). It now had a license plate and was street legal. I drove it around here and there, just having fun. Local store runs and what-not. No problems at all.

Now that it was running, I figured I would make it look a bit more presentable (keep in mind, I had no idea at the time how ridiculously damaged the variator/clutch assemblies were...again, new to this stuff). I decided this would be the perfect time to give painting a try (compressor...hvlp paint gun, etc...). I ended up with this:



Yet again, I was patting myself on the back, quite pleased with the end product.

It looked a bit nicer so I started riding it around a bit more. My first long ride (10km round-trip) left me stranded on the side of the road on the return trip. It just died while going up a long hill at WOT. I had no idea what the problem was (yet again....new to this stuff). I didn't have an air filter on it (don't laugh please...I now know about the dumbness of not having an air filter on a 2T) as the stock box was missing when I purchased it. I just assumed something had gotten into the carb and just clogged it up. I took it home, cleaned out the carb and it started up again.

Ok...aftermarket air filter purchased and installed. I go out on another trip and the engine dies just a few minutes from home...I was close, so I pushed it back home (never again!!!). I was too tired from pushing it home that I decided just let it sit til the next day. I tried to start it the following day with no love...cleaned out the carb and all was good.

So, I brought it to a local shop that deals with scooters and ATV's to try and get some info and find out what the problem might be. I had them glance over it and then started asking questions, only to learn that the oil pump system had been bypassed by the previous owner. I had seen a cable tied back but never realized what it was (cable to oil pump from y-split throttle cable). The previous owner had been running pre-mix and I didn't know it. Ever since I got the thing running I had been putting pure gas through it...NO OIL! Now things were starting to make sense. I now understood why the 2 stroke oil never seemed to go down in it's separate tank and understood why it would die (hot anyone?). I'm just surprised the engine never froze up.

Well...Now we're coming up onto current events. I wanted to start replacing parts. After a lot of research, I finally learned that the engine was a minarelli clone, so I purchased a few parts...complete clutch kit, complete variator kit, CVT belt and a 70cc upgrade kit. It already had a Keihin aftermarket carb on it that I now know is a PE20 (I thought it was a PE22 up until yesterday when I learned how it should be properly measured to find out the size...INSIDE the venturi).

Damn..this story is getting long..sorry! I just like to be thorough with the info.

Soooo, the 70cc kit and variator kit are in and the 70cc kit is installed. I'm still waiting on the clutch and belt to come in so that I can install everything on that side.

Now, to my main question...jetting. I've searched the net only to find a million different opinions. I've got the basics down (I think) but I still have a problem. This Keihin carb currently has a #95 main and a #42 pilot installed. I don't know if these were the original jets when it was purchased new. The previous owner said the engine was bad...was it due to bad jetting? I don't know. I don't know what the jets were on the stock carb (I don't even know what the stock carb WAS) so have now base to start from. I'm not sure where to begin with jetting this. I want to buy a set of around 5 jets and go from there, but I don't know what range of jets I should buy.

The engine will have the following mods when all is said and done:

70cc upgrade kit
Keihin PE20 carb
what I BELIEVE is the stock exhaust with an aftermarket silencer (not sure if this makes a difference).
Prodigy variator kit (a set of 5g and 6g rollers were included to choose from)
stock clutch assembly with stock springs (again, not sure what the spring specs are as they're stock)

Here is a pic of the exhaust to clear up any questions on that:



So, anyone want to dive in and give me a few leads, tips, pointers, knocks on the head for being stupid? I'm open to everything at this point!!

Thanks in advance!

 

update...

Ok, after only about 10 minutes of searching I have one source that quotes the stock carb on the minarelli 1PE40QMB to have a #75 main jet. Again, this is a clone so I don't know if that info is good. But, it could be a start.

 

I think the jetting in the PE will be close. Might need a bigger main.
I'd run it and see how the plug looks.

 

Your input is MUCH appreciated!

If I wanted to go with a close-nit range of jets to play with, what would you suggest? It idled perfectly fine before any of my changes, so I'm assuming the pilot jet is good to go?

 

Very nice man, in the words of Aaron Kaufman from Fast and Loud, "motors just want to run" and I think few people realize how easy they are to get moving again. It's just Air, Fuel, and Spark. Your restore is completely sick. I bet you could find a stamp on the motor at the very bottom, on the side, under the clutch housing.

 

On my race motor w/pe20, pilot is 45-48 main is 115-125.
Maybe up 1 on the pilot and a cpl up on the main. It's all a guess till it's running.
I'm leaning toward that pipe being aftermarket but I can be wrong. It'll prolly be fine.

 

Thanks. Since I'm waiting on the other parts, I decided to tear it completely down so that I can sandblast the frame. There was lots of surface rust, but that will all be taken care of.

As far as a stamp, it was a no-go. I found some SMC specific numbers, but nothing that would identify the engine, as far as getting aftermarket parts is concerned. It's like they didn't give the engine a name...just the ATV as a whole. I've got PDF parts lists for the ATV as a whole, so that will do for OEM parts. A Taiwanese seller on eBay (autotech355) helped me quite a bit with info on what aftermarket parts to look for, so I should be good from here on out.

Excellent. Thank you very much. I'll pick up/order some jets in that range and have them ready for when the other parts come in. I'll more than likely be updating this thread hopefully within a week (yeah, that's code for 'asking more questions').

Thanks again!

 

would you mind sending the .pdf to me? screen name@yahoo.com

 

For you and anyone else that may need it:

http://www.ering.at/media/Daten/Publ...1_Partbook.pdf

 

It's called the 'Bullet 50' in some European locations.