|
Post by renohal77 on Jul 16, 2021 19:28:34 GMT -5
I have a Taotao qmb139 knockoff that I bought in 2012 and it's been one helava scooter...right up until I tried to upgrade it last year. I got a 100cc bbk (50mm) (I know it's not really 100cc) off of Amazon and installation wasn't all that hard. I did the upgrade with the help of many Youtube videos. Did a lot of learning. It ran great or it sounded great. Ran smooth and had lots of power. Problem was after about 4 miles, it overheated to the point the oil turned dark grey and had the consistency of water. I changed the oil 2 times and figured if I had to change the oil this many times it would not be worth it. So I started taking the engine apart to see if there was anything wrong. I found a cracked rocker arm assembly and the metal head gasket was broken in 3 places. The pipe going to the muffler now looks like a rainbow because of the heat. The gasket around the cooling shroud was all broken up and hard. I went ahead and reordered a new cylinder block with piston, head, cooling shroud gasket and rocker arm assembly. While waiting for this stuff to come in the mail, I posted on a scooter forum (can't remember which) the problem I've been having. Literally the only response I got was try a new oil pump. So I ordered a new one. Installed all of it making sure everything I did was exactly how the youtube videos showed to the tee. Again, same exact problem. Gasket for the cooling shroud was completely melted this time and the oil was dark grey after only 4 miles (distance to my work from home). Oil is now leaking from somewhere behind the flywheel. It kind of looks like it actually might be coming from one of the bolts that hold that half of the engine together. Not totally sure but it doesn't seem to be coming from the seal around the crankshaft itself. I've got a gasket set on its way so I'm just going to replace that gasket. So the only thing I can come up with is 100cc bbk is too much compression for a qmb139 engine. But also, why is no one else complaining about this. I don't see anyone in any forums having the problems I'm having. There are so many more 100cc bbk's available than 70, 80 or even 50cc kits. I'm in the process of purchasing an 80cc bbk (47mm) to see if maybe that will be better but I wanted to post on here in case anyone had any ideas before I installed it. I'm not too far away from just driving this scooter off a cliff and just give up on these damn things. The amount of money I have spent trying to do this myself I probably could have had someone do it professionally. I am so fn frustrated right now. That being said, any help will be greatly appreciated.
|
|
|
Post by scooter7878 on Jul 16, 2021 21:24:47 GMT -5
Did u change the carb or main jet one of the main things that cause overheating in a air cooled engine is running lean meaning to much air to fuel ratio. I'm in Florida sea level if I go from stock cylinder to a 50 or 52 mm piston kit I'd go up to a 95 main jet or even more. Stock main jet is 78 usually so depending on exhaust upgrades and air filter upgrades u should be over a 90 main jet. Another thing that causes hot is a air leak which give u a lean condition also. Any kind of vacuum leak will cause that like a intake manifold leak or a vacuum hose off
|
|
|
Post by scooter7878 on Jul 16, 2021 21:32:44 GMT -5
If u have any questions regarding jetting feel free to ask me but even with a 47mm kit u will still over heat if not rejetted I'd advise just buying a performance carb and a jet kit so u have a assortment of jets to tune it properly most of the stock carbs u have to drill the screws in the carb brown to remove them and the air fuel screw has a plug over it that has to be removed in order to adjust it I recommend getting a carb 20mm carb from a reputable place like parts for scooters, racing planet, or ncy store which is who I use they are great have good prices and are super responsive and helpful. Naraku makes a great carb there about 75 bucks but worth the money
|
|
|
Post by scooter7878 on Jul 16, 2021 21:42:49 GMT -5
If u overheated that bad again ur probably going to need a new cylinder again unfortunately. I use a seller on Ebay called parts scooters to go. Hes got 50mm cylinder and big valve head and a airsal domed top piston which increases compression and power for 120 I believe and it comes with a new rocker assembly. the airsal piston is a great piston as it increases compression and it's also a good bit lighter than standard pistons which reduces strain on the stock crankshaft from the up and down movement at high rpm. The stock cranks is usually the first thing to fail with a 50 plus kit it's just not meant for that power and weight of the heavier piston the big valve head that comes with the kit is specifically made for the airsal domed piston it's a great setup
|
|
|
Post by renohal77 on Jul 18, 2021 9:54:18 GMT -5
Did u change the carb or main jet one of the main things that cause overheating in a air cooled engine is running lean meaning to much air to fuel ratio. I'm in Florida sea level if I go from stock cylinder to a 50 or 52 mm piston kit I'd go up to a 95 main jet or even more. Stock main jet is 78 usually so depending on exhaust upgrades and air filter upgrades u should be over a 90 main jet. Another thing that causes hot is a air leak which give u a lean condition also. Any kind of vacuum leak will cause that like a intake manifold leak or a vacuum hose off I'm pretty high up here in Reno, Nevada. I did change the main jet. I tried the 95 and it was literally spewing gas out the muffler so I went with a 90 and that seemed to be perfect. I am running it a little rich to try and cool it down but it doesn't seem to be helping at all. It's at the point it kind of bogs down a little when it's cooler out but doesn't die. I did upgrade the muffler and air filter. This is the kit I installed: AmazonI never thought of a vacuum leak. All hoses are connected with no cracks in them. I'll have to look into that further. Thank you for your suggestions. You gave me something to look into!
|
|
|
Post by scooter7878 on Jul 18, 2021 14:26:02 GMT -5
U can spray with carb cleaner while it's running and listen for a rpm change also check ur vaccume fuel petcock make sure it flows good and I'm assuming ur fan is in good working order and all 3 fan covers are on u can buy a upgraded cooling fan but I really can't think of anything else that would cause that kinda of overheating. A exhaust leak will also cause u to run hot.
|
|
|
Post by renohal77 on Jul 19, 2021 9:13:34 GMT -5
U can spray with carb cleaner while it's running and listen for a rpm change also check ur vaccume fuel petcock make sure it flows good and I'm assuming ur fan is in good working order and all 3 fan covers are on u can buy a upgraded cooling fan but I really can't think of anything else that would cause that kinda of overheating. A exhaust leak will also cause u to run hot. Just trying to eliminate potential problems I did get an upgraded fan. Also, good thing I got an extra gasket for the cooling shroud as the last 2 were melted. I saw a video on YouTube using starting fluid to find a vacuum leak so I'm going to try that this morning. Thank you for all your help. I really appreciate it. Hopefully this will be it. I will let you know.
|
|
|
Post by renohal77 on Jul 26, 2021 16:49:53 GMT -5
We'll, this took a while to get to thanks to the wildfires we're having in the West but I was able to check today and there are no vacuum leaks. I checked every vacuum hose and the intake manifold with starting fluid. I thought it would have been the intake manifold but it was fine. I'm not sure what to do at this point. The spark plug is getting a little black since I've been running it kind of rich to get the temperature down a little. Thanks for your suggestions. Hoping someone might have another idea.
|
|
|
Post by scooter7878 on Jul 26, 2021 17:34:21 GMT -5
Boy idk man it seems u pretty much ran down everything. I got a 50mm kit with a stroker crank and big valve head in mine I live in Florida it's been like a 100 degrees er and I run hard all day and I have no overheating issues its def not that a qmb cant handle a 50mm kit. One thing that get me about what u just said is that it bugs when its cooler out which to me indicates a leaner mixture because a motor requires a richer mix with cooler air temps. What carb are u running stock? If so ur main jet may be ok but theres a needle adjustment which adjust the mixture between 1/4 to 3/4 throttle and in most stock carbs it's not adjustable. Maby ur lean in that range causing the overheating. If ur still running the stock carb I would suggest at very least to get a 20mm carb performance carburetor off Amazon or ebay but really recommend to get one from a real scooter shop online. ncy ,parts for scooters, racing planet scooter tuning are all good I recommend the naraku brand but it's like 75 compared to 30 off Amazon but the needle will be adjustable on any performance carb weather from Amazon or the other places
|
|
|
Post by scooter7878 on Jul 26, 2021 17:36:40 GMT -5
Theres really not much but fuel mixture on the air cooled motors gonna cause overheating as long as ur fans working but the bog when its cooler out tells me at some point ur probably lean if it was too rich it would bog worse at hotter temps and be better with cooler temps
|
|
|
Post by scooter7878 on Jul 26, 2021 17:39:25 GMT -5
One other thing u can try also it run a ngk cr8 hix plug instead of a cr7 it's a cooler plug maby u got pre ignition causing high temps
|
|
|
Post by renohal77 on Jul 26, 2021 21:13:37 GMT -5
The carburetor came with the BBK I ordered. I can't really tell a difference between this one and the stock. I just figured it was newer so I threw it on. I think I will see about a performance carburetor. Tomorrow I think I'll take apart the carb that's on there and make sure the needle isn't adjustable, first. I appreciate it. You're giving more options to think about. This is just driving me absolutely bonkers right now...lol. I'll keep updating.
|
|
|
Post by scooter7878 on Jul 26, 2021 22:18:53 GMT -5
The carburetor came with the BBK I ordered. I can't really tell a difference between this one and the stock. I just figured it was newer so I threw it on. I think I will see about a performance carburetor. Tomorrow I think I'll take apart the carb that's on there and make sure the needle isn't adjustable, first. I appreciate it. You're giving more options to think about. This is just driving me absolutely bonkers right now...lol. I'll keep updating. . Idk if u know but just to be sure move the clip down one notch at a time. Clip up =leaner clip down=richer some times after u adjust one part of carb u need to change other setting like the air fuel screw or sometime I find a better jet in either side but only do one adjustment at a time and drive some to see to many adjustment at one time can get u all turned around going crazy
|
|
|
Post by scooter7878 on Jul 26, 2021 22:21:25 GMT -5
Do a plug chop at wot if u don't know how Google it but u will need a way to cut the threads off the plug and be sure to use a new plug only for the wot run warm it up first with the plug that's in there
|
|
|
Post by renohal77 on Aug 4, 2021 12:35:53 GMT -5
I adjusted the needle one notch down but I don't notice a bit of difference. Still bogs down a little in the morning and not at all during the afternoon. I cleaned the spark plug until it looked like new and after exactly 20 miles it's a little dark but no white on it at all. I adjusted the air/fuel ratio a little but I really don't think it needed it. Seems the needle adjustment did nothing so I'm not sure if that's a problem or not. Here is a picture of my oil after 20 miles. Seems there is a little more viscosity this time than the last oil change after only 10 miles. The last couple days have been exactly 100 degrees and in the morning to work, around 65. At this point, my patience and my budget for this is pretty much non-existent. I don't even want to look at this scooter any more. I think I'll see about putting a 50cc rebuild kit in and sell the f***** thing and get something I don't have to upgrade myself. I appreciate the suggestions you've given me to try and get this going but I think I'm done. I just wanted something with a little more get up and go but this has just turned into a mentally exhausting project that never worked out.
|
|