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Post by pmccolley on Jul 16, 2012 19:16:15 GMT -5
Just picked up a free scooter on CL last week. The story was it ran fine for 1600 miles then it wouldn't start one day. They thought it was a carb issue. So it sat for a few years then posted for free on CL
After getting it home and looking at it the carb and everything has been looked over and I assume tinkered with.
I pulled the tank and flushed everything out as well as the lines and sprayed the carb with cleaner and cleaned the bowl. It does crank over but I dont hear anything like its firing. So I pulled the plug and it is wet but no spark. Testing the plug wire to the frame I got spark so I bought a new plug and it has bright blue spark on it now.
I tried to start it again and eve used a little starting fluid with the aircleaner off and still not firing just cranks over.
I pulled the card and check the reed valve to make sure nothing was bent or broken and everything looks great. It still has the steel reeds installed (2 fingers on each side).
So I feel like the motor should be getting the 3 things it needs to run but the combustion process is not working.
I have not tested compression yet as I need to pick up a gauge.
Looking for any guidance or suggestions.
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Post by 90GTVert on Jul 16, 2012 19:34:09 GMT -5
 Sounds like you're getting to the other major player, compression. Look for 100psi as a minimum. If it's got spark and is not even trying to fire with starting fluid and the air cleaner off, it's likely the problem. This won't cause it to not start, but if it's really been sitting for a few years, I'd check the 2T oil in the reservoir and consider replacing it too for good measure. Might wanna wait to see if it runs first though. I'd also suggest replacing the gear oil. |
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Post by Fox on Jul 16, 2012 19:36:56 GMT -5
Compression issue most likely. I had a QJ1E40QMB a few years back that had spark and what seemed like compression but refused to fire and it turned out it was a bad top end due to a connecting rod bearing failure. There was compression but the piston was so sloppy in there it was weak. Replaced the top end with a used stock one I pieced together from a couple of the guys here and it ran great after.
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Post by pmccolley on Jul 16, 2012 23:50:50 GMT -5
Well got a chance to get out the compression tester and got 95psi with the electric start and lost 5psi to 90psi with the kickstarter.
This is my first foray into scooters and small engines.
I assume the next step is to tear down the engine? Do I just need to look at the cylinder head, piston and rings or are there other things to consider as well.
**Update**
Ok so this may be a dumb question but do I need to have the reed valve and carb installed to get an accurate test pressure?
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Post by pmccolley on Jul 17, 2012 0:19:36 GMT -5
So looking around at parts, I am seeing direct replacements and big boar kits. Is now the time to consider doing one of these Kits? Advantages\Disadvantages? My wife will probably be riding this scooter all of the time. I am a big guy and over capacity lol so I probably shouldn't stress the frame ehh. Or are the limits just for the engine power, belts, shoes etc.
Thank you for all your input.
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Post by 90GTVert on Jul 17, 2012 6:40:32 GMT -5
You don't need the carb and reeds installed to do a compression test.
Next step is to tear down the top end and look around.
A 70cc BBK should give a nice increase in power. I'd stick with an iron cylinder rather than aluminum and I'd steer clear of the cheapest kits out there. Some don't even come with a cylinder head to match the new bore. Polini Sport, Hoca from PFS , and a kit from Autotech355 on eBay are a few examples of good and reasonably priced kits. As long as the additional cost is not an issue, I'd go with a BBK instead of a stock bore. The down side would be anytime you create more power, you are at risk of reducing engine life. The sport level iron kits like I listed should not have a major effect on engine life though, as long as it's tuned properly. The other down side I suppose is that you need to tune the carb and possible the CVT when the BBK is added. You'll probably have to upjet the carburetor slightly and possibly make idle mixture and needle clip adjustments. You may need to change roller or slider weights to get the best performance. IMO that's all worth it for the extra power.
I dunno what the weight limits are for. I assume the frame. I'm 300lb and have 3 scoots and I ride the hell out of them all.
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Post by pmccolley on Jul 17, 2012 13:02:58 GMT -5
After reading the followup post this morning I took a few minutes before work to look at the kits you mentioned. I did see that I need to identify the wrist pin size. I pulled the plastic cover, all the bolts on the metal cover and kick start pedal off. Do I need to remove the lock ring on the kick start input shaft to get the cover all the way off? Since I couldn't get it off I assume that would be a yes but again for a lack of tools I need to pick up lock ring pliers after work.
Now to remove the head do I need to remove the engine or are there any easy tips on this process?
Last looking at the kits, Autotech355 appears to have a great price and fairly complete 70cc kit. But I only see the kit in the 10MM size and from all the reading I have been doing I believe mine is a 12mm but that is why I am trying to open the cover and count the splines on the variator.
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Post by nitroman666 on Jul 17, 2012 13:15:48 GMT -5
You do not have to remove the kick start assembly from the cover. There are some anomaly 40qmb engines out there, the only real way to see what wrist pin size you have is to remove the top end and measure it.
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Post by Fox on Jul 17, 2012 14:45:34 GMT -5
If you removed all the bolts holding the cover on there then whack the cover on the back end with a rubber hammer to break the seal on the gasket and it should pull off easily. There's a bolt in the center of the cover that has to come out.  Once you get all the plastic off the engine it'll look like this:   Then just remove the 4 nuts on the head and the whole top end will pull off. You may have to hit the cylinder with the rubber hammer to break the seal on the base gasket. Then there's two little clips that hold the pin in the piston. You remove one and the pin will slide out releasing the piston from the connecting rod and then you'll be able to measure it. |
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Post by 90GTVert on Jul 17, 2012 15:36:06 GMT -5
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Post by pmccolley on Jul 17, 2012 19:07:17 GMT -5
I am heading home now so I will give a a try, I had all the bolts out including the center bolt and it seemed loose I have maybe 1/16 to 1/8 space between the top of the cover and gasket. I just didnt want to force it and break something. Sorry I missed the video on the cover removal, I watched at least 30 on your youtube channel yesterday.
Glad I checked I was just about to hit the tool store. Maybe I still should.. lol
But it does look like I need to remove the motor to get the head off, correct?
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Post by Fox on Jul 17, 2012 19:20:59 GMT -5
There are two locating dowels on there that can sometimes make removing the cover a pain. If you are confident you have all the bolts out then grab the kick lever and give it a good yank.
It's difficult to say if removing the engine is a must or not due to a lack of pics but it sure can't hurt.
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Post by 90GTVert on Jul 17, 2012 19:33:35 GMT -5
Some scoots you can work on the engine with it in the scoot and some you can't. Usually the long frame scoots you can, short frame you can't.
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Post by pmccolley on Jul 18, 2012 16:15:02 GMT -5
It was the locating dowels they were very tight.
I am going to be wiping a reloading my PC over the next day or two so I hope to get to the scooter this weekend. I will be able to post some photos then.
The scooter is a 2005/2006 era Baja Motorsports BR50 made by QJ model qj50qt-5. I tried talking to BM about the service guides\manuals early on who swore the scooter was a clone and not theirs. Later they find out that it was probably to only 2 stroke that was imported by BM into the US and sold as they removed and reinstalled all 2 stroked with 4 strokes as I was told by their staff. The scooter itself looks almost exactly like your Keeway Venus with the retro look.
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Post by pmccolley on Jul 23, 2012 15:40:42 GMT -5
Well I just have not had the time to tear this thing down and get the wrist pin size. Combine that with temps here in the 100s lately working in the driveway is not much fun. I was looking at your thread on checking the wrist pin sizes and was wondering how reliable is the drive boss method of sizing the wrist pin. 49ccscoot.proboards.com/index.cgi?board=yamajog&action=display&thread=2422Should I rely on this method to order parts or should I really just take some time and tear it down first? Thank you everyone for all your help. |
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