139qmb engine test by rotating cooling fan?  By  gift (Read 5,043 times)

You can rotate the engine by turning the fan and that doesn't mean it is bad . if it rotates very easy you may have low compression but that doesn't mean the engine is shot. All that means is it may just need new piston rings or a top end rebuild . I suggest you do some tests and take some video of it so you can post it on here and we can talk you through what may or may not be wrong. I can rotate my engine by turning the fan , its kind of hard to turn on the compression stroke but u can still turn it over.

If you are up for it , an willing to do a little work , I would get the valves adjusted correctly , replace the spark plug , make sure the battery is good and charged ,get the carb cleaned and see if the scoot will turn over . if it turns over but do sent start , you will want to check to make sure you have spark . if not it could be as simple as replacing some electrical components . most of the work on these scoots are bolt on , or plug 'n go . some you will have to use certain tools for , like to check valve clearance , and you will want to make sure the engine is in time " which is all pretty easy to learn " . there are many videos u can watch that will take through each process step by step .

I'd ask him what exactly he did to determine that the engine was "bad". It'd be nice if they were a little more specific. Someone saying the engine is bad without telling me what exactly is bad with it, doesn't cut it with me.

I am totally up for it but I first need to get tools ready I think. I got an email from Harbor freight that they will have sale starting tomorrow so I will go there and get some tools ( I think I will need a electric impact wrench first thing. I tried to unbolt a nut last week with a manual socket wrench, it did not move a mm.) Could you recommend some other special tools I would need? I have some basic tools which now get me to the inside of the scoot. I have removed all the plastic frame last week actually I took the carb out and planning to adjust the valve and clean it this weekend.

Actually Mechanic at the shop unbolt many things when they first tried to figure what is wrong with it so I need to reconnect everything back first in order to try to crank it up. I actually plan to just open up the top end of the engine to inspect inside but could not get the engine out yet because of that bolt. 

I rotate the engines on both my 50cc with a BBK and my stock 150cc by hand using the plastic fan every time I set the valves, so that is definitely not a test that will determine the engine is bad (unless you cannot turn it at all, which would mean it is seized).

Take some pictures of it once you get the plastics off, let us see decent shots up close and from a few feet away from every angle, or better yet take a video of it SLOWLY moving around the engine and post it to youtube then click the movie icon in the reply box and paste in the URL from youtube.

We are going to need to check the tubes, so run the video/pictures along the tubes. Good pictures of the carb and it's attachment points are also important.

Once we can look it over and see if there is anything obvious, we can take it STEP BY STEP GUYS (don't everyone throw out ideas at once, it will overwhelm the OP). The three basics for a gasoline engine are fuel/air, spark, and compression. We will make sure each is performing properly one step at a time and get this scooter running!

BTW- $300 installed for a new engine is pretty cheap, that's basically the price of a new engine without including labor, so I kind of wonder if this shop was truly going to replace it, or swap it out for another used one and fix a small issue with it to do the same to the next customer? If that price doesn't include labor, then it's more likely to be legit, because they would be charging more like $450-500 total.

yeah ok i agree... guess i was picturing rotating the engine by attempting to get my fingers around the nut with the fan cover on. i would have a hard time just getting one finger in there and then trying to rotate the engine would be difficult.