BBK Issues

chopyouup · 07-16-2014, 02:53 PM

Hello, new to the forms so let me introduce. I have 2 scooters a 150cc johnway and a 50cc bintelli scorch both were non functional when purchaced and with help from this form I have got the 150 running great.

The bintelli 50cc is a bike I am working on for my wife. At stock it seized, was able to free it, but began burning engine oil (seize originally from low oil possibly not filled at the shop I bought it). Bought a 60cc bbk to replace what i assumed were blown rings and piston and installation went smooth. When I rock the flywheel l around top dead center I get a clang, possen the 6 bolts holding down the jug and the flywheel spinns smoothly no clang.

Right now I have it all bolted down and valves set to 0.005 and I can get it to run but the clanging repreates at every rotation of the engine. No idea what is going on.

I tore it down (top end) and re went through the steps get to the end again and same thing, I can't leave the top end unsecured but the clang I here and feel can not be good. Its almost like I need anothrr couple mm of space in the top end ( but everything both gaskets are installed)

Thanks!

- Carl

Madathlon · 07-16-2014, 04:13 PM

If it seize chances are that the Rod bearing at the crank is also bad. (Unlike a car there no separate bearing there its the rod it self. You will most likely need a new crank and Rod to fix that.

chopyouup · 07-16-2014, 04:27 PM

Would that be true even though I am able to start it?

Its almost as if its to tight, normally as you turn the engine over it sits into top dead center, mine feels like it has to push through something and when you force it through TDC it makes the clang/forcefull. Again if I loosen the top bolts it turns over smoothly...

Wrisberg · 07-16-2014, 06:22 PM

Try measure the squish out?
EEither your bbk is made wrong, with to little (none) squish, or, it could be the button end bearing in your conrod.
Try taking the top end of, and feel for clearance when holding a finger on the piston and turning the flywheel each way. There should be none.

Wrisberg · 07-16-2014, 06:23 PM

If you take off the camshaft, and cranks the engine, does it run free and without noices?

Madathlon · 07-16-2014, 07:05 PM

Yes it can run with a bad rod bearing, and with every revolution it is causing more damage. Any time you seize a motor you should do a full tear down and inspect everything. The hidden damage can cause even more damage to new parts. Like a pistion slapping a head can crack it, it can stretch the head bolts/rods. It can bend valves and even cause a denotation of the whole top end. (Turn it into a grenade)

chopyouup · 07-16-2014, 07:42 PM

OK tore it down again, talked to a mechanic who said it might be an issue with the piston hitting the valves. Took it apart looked at the head and the piston and it looks pike the piston is coming a bit to far out and hitting the head (wear not on valves but the area around it appears to be where the piston is pushing into the head. I was advised to try and put a second head gasket in to increase clearance.

Madathlon · 07-16-2014, 09:04 PM

No, take it farther apart and check the rod and crank. If the piston is hitting the head chances are its lose on the crank from wear.

chopyouup · 07-16-2014, 10:10 PM

I know what you meant but cracking the gearbox is not a single thing, I would rather rule out simpler causes before that.

The seize I had was a soft seize that is as the engine cooled it would come free again. The engine was not entirely without oil just low less then .3 oz which should be enough to have been coating the bearings. I also while the jug was out played with the crankshaft for play while holding the flywheel and did not feel any. I would not be surprised if this issue is simply the stock arm plus the new piston is just a few mm higher then the replacement bore I installed, the bore kit did NOT include a new head, in the head there is sort of a dome where the valves and spark live, a proper 60cc head probably fits just fine, but like I said I am using the stock 50cc head and I can see in the head the wear the piston was putting on it.

chopyouup · 07-16-2014, 11:36 PM

Quote:

Originally Posted by Wrisberg

If you take off the camshaft, and cranks the engine, does it run free and without noices?

No no noise. And ilwith the head off the piston rises (its dined) above thejug a tiny bit.

chopyouup · 07-17-2014, 06:13 PM

OK so slapped on 2 head gaskets, the original plus the bbk one ( the original had to be enlarged and smoothed so it would not run into the piston. I appear to be getting good compression and can fire up the scooter. I no longer have the push through feeling at TDC. While it is possible the bearings could have damage I will let it ride for a while and see if performance or noise changes.

07-16-2014, 04:13 PM	#2
Madathlon Join Date: May 2014 Location: Redding, Ca Posts: 70	If it seize chances are that the Rod bearing at the crank is also bad. (Unlike a car there no separate bearing there its the rod it self. You will most likely need a new crank and Rod to fix that.
	0

07-16-2014, 06:22 PM	#4
Wrisberg Join Date: Jul 2014 Location: Downtown Posts: 11	Try measure the squish out? EEither your bbk is made wrong, with to little (none) squish, or, it could be the button end bearing in your conrod. Try taking the top end of, and feel for clearance when holding a finger on the piston and turning the flywheel each way. There should be none.
	0

07-16-2014, 07:05 PM	#6
Madathlon Join Date: May 2014 Location: Redding, Ca Posts: 70	Yes it can run with a bad rod bearing, and with every revolution it is causing more damage. Any time you seize a motor you should do a full tear down and inspect everything. The hidden damage can cause even more damage to new parts. Like a pistion slapping a head can crack it, it can stretch the head bolts/rods. It can bend valves and even cause a denotation of the whole top end. (Turn it into a grenade)
	0

07-16-2014, 07:42 PM	#7
chopyouup Join Date: Jul 2014 Posts: 11	OK tore it down again, talked to a mechanic who said it might be an issue with the piston hitting the valves. Took it apart looked at the head and the piston and it looks pike the piston is coming a bit to far out and hitting the head (wear not on valves but the area around it appears to be where the piston is pushing into the head. I was advised to try and put a second head gasket in to increase clearance.
	0

07-16-2014, 09:04 PM	#8
Madathlon Join Date: May 2014 Location: Redding, Ca Posts: 70	No, take it farther apart and check the rod and crank. If the piston is hitting the head chances are its lose on the crank from wear.
	0

07-16-2014, 10:10 PM	#9
chopyouup Join Date: Jul 2014 Posts: 11	I know what you meant but cracking the gearbox is not a single thing, I would rather rule out simpler causes before that. The seize I had was a soft seize that is as the engine cooled it would come free again. The engine was not entirely without oil just low less then .3 oz which should be enough to have been coating the bearings. I also while the jug was out played with the crankshaft for play while holding the flywheel and did not feel any. I would not be surprised if this issue is simply the stock arm plus the new piston is just a few mm higher then the replacement bore I installed, the bore kit did NOT include a new head, in the head there is sort of a dome where the valves and spark live, a proper 60cc head probably fits just fine, but like I said I am using the stock 50cc head and I can see in the head the wear the piston was putting on it.
	0

07-17-2014, 06:13 PM	#11
chopyouup Join Date: Jul 2014 Posts: 11	OK so slapped on 2 head gaskets, the original plus the bbk one ( the original had to be enlarged and smoothed so it would not run into the piston. I appear to be getting good compression and can fire up the scooter. I no longer have the push through feeling at TDC. While it is possible the bearings could have damage I will let it ride for a while and see if performance or noise changes.
	0