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Discussion in 'Motorized Bicycle General Discussion' started by pechroc1, Sep 23, 2010.
what are the long term effects of an air leak?
A flat tire.
dont take long before you no go any more..!
that is if we are talking about the engine and not the tire.....!
if it's the tire you will be pushing it before long...
An air leak will cause your engine to run very lean on fuel in comparison to the amount of air the engine is getting which will make the internals get very hot and in a short matter of time the engine will be trashed and need a rebuild if it is even rebuildable after it quits.
So as you can see it's a very bad thing to run with an air leak.
^^^^^^ thats me! awesome!!!!!!!!!!!!. i think its about time for a rebuild.. ...
so were do i start to rebuild? crank, piston, cylinder? it didnt quit yet but its on its way out. i took apart the top end but i dont know waht to look for...?
When you say on its way out what do you mean?
Example: low compression or no power or knocking noise or very hard to start.........?
How exactly is the engine running?
What makes you think it's on it's way out?
Need a little more info. so I can direct you in the most practical way to move forward on this issue.
low power, rattling noise coming from the cylinder /head when revved. runs very very hot. after a few minutes of running it bogs down. the spark plug looks light brown.
How long have you been running this motor?
what makes you think you have or had an air leak?
and if now fixed where was it and how didi you fix it?
What is your experience level regarding these engines or any engine as far as rebuilding 4stroke or 2 stroke engines?
Has the engine ever completely siezed up on you?
ive been running it for 3 weeks and much of it with the leak without me realizing it.(im a newb to most things mecanical) really started to notice the effects the past 20 miles or so before trying to understand whats was going on(what a dumbass) the leak is not fixed. i have a new carb coming tomorrow.
the engine has not seized. just boged down. it stills starts right up. and my experience is taking this thing apart yesterday... thats about it. i didnt have a gear puller so i couldnt pull the bottom end apart. but i was able to pull the head cylinder and piston, apart. the only thing i noticed was it looked like something was rubbing the piston by the exust port as the piston had some slight indentation by the exhaust manifold.
this leak started with a cracked carb body the i repaired....(i Thought... HA!)
It is possible that your engine is not toast yet, but if it is then you may just consider a replacement engine if your mechanical skills are few att his point, if you do ahve a good assortment of tools and a good place to work, you may want to tackle a rebuild but if you have to replace more than just rings, gaskets and the cylinder you can purchase a new slant head engine from BGF on ebay for less than the cost to completely go through the one you have now, it reall yjust depends on what is needed in the rebuild, if it has never completely siezed up on you then it's very possible that a basic top end rebuild could get you running good and strong again.
Heres links to the replacement engine alone I spoke of above 4 types Black slant head, Chrome slant Head and standard straight plug engine all good choices in my opinion:
Motorized BIKE GAS ENGINE - 80cc motor EPA black slant - eBay (item 190441041812 end time Oct-06-10 18:02:15 PDT)
Motorized BIKE GAS ENGINE - 80cc motor EPA slant Chrome - eBay (item 150486198351 end time Sep-27-10 13:22:17 PDT)
Motorized BIKE GAS ENGINE parts - 80cc motor EPA black - eBay (item 170378494424 end time Sep-26-10 17:27:46 PDT)
Motorized BIKE GAS ENGINE parts - 80cc motor silver EPA - eBay (item 170494273408 end time Sep-29-10 22:06:52 PDT)
i really appreciate this. just for my knowledge what happens to the top end..? does it warp, do the rings blow out? what happens. should i look for something in particular? thanks for your help brother.
If piston is scared that means the cylinder is also and that is not good, here are the parts you will need to rebuild the top end if that is all you need and it sounds like you may have a rebuildable engine there.
bicycle Motorized BIKE GAS ENGINE 80cc 66cc cylinder - eBay (item 190412778331 end time Sep-30-10 00:21:23 PDT)
bicycle Motorized BIKE GAS ENGINE 66/80cc full gasket - eBay (item 190438262254 end time Sep-30-10 14:27:22 PDT)
bicycle Motorized GAS ENGINE needle bearing w rod, clip - eBay (item 190355382041 end time Oct-01-10 00:54:25 PDT)
PK80 80cc Alloy Chrome Piston
80cc Piston Ring Set
No problem, we all need a little help some time, and these little engine as simple as they are can still pose problems for us all some time.
Ok, if you noticed a scratche darea on the piston where it passes the port that is a sign of something that has likely got hung between the piston and the cylinder wall which is not good, if it had broken the piston ring the engine would have quit on you very suddenly, but since it didnt you got a little more running out of it.
sounds to me like your best bet is a top end rebuild, in the previous post you will find what I think is the best & cheapest source for all the parts you will need to do the rebuild.
Question: does the piston thats in your engine have a slight domed up shape on the top of it?
This is very important to know because some of the straight plug head engines had a piston that is almost flat on top and as far as I know all of the slant head with spark plug that screws in at an angle have the domed piston, if yors is the domed piston engine then the link for the piston I gave you will work just fine but if yours looks almost flat then it will take a different piston which BGF carries.
I will be back on here tomorrow at around 7:00PM Central standard time, as for now it's 11:15PM and I have to get up for work @ 4:30AM so it's my bed time now, look over the parts links I gave you and crunch some numbers, then you will have a better idea of the route that fits your needs the best, we will continue this if need be tomorrow evening, feel free to Private message me if you wish about any of this or we can just keep going with it right here until we get you up and going again.
There may be others here that can give you some good advise on your options as well, theres some great people on here that know more than I do and always have some great ideas.
Good Night all.....and God Bless
you the man ttys!
Before breaking down the engine, I would check to make sure that you aren't just running too lean. At one point I was running my engine with too small of a jet and it would bog down/ get too hot. A light brown color plug indicates a lean condition. All of these engines make rattling noises. Mine rattles a TON when revved but this is in fact coming from the clutch.
If you order all of these parts and end up not needing a rebuild, then it will be a waste. I would make sure to correct your fuel to air mixture first before breaking down the engine.
will do. however, my clutch never made this noise before and even with the clutch housing plate off and my ear to the case it doesnt seem to be coming from there. but im not buying anything till i get it together with the new carb on.