Problem With My Top End

[CranbrookKid]

I about a month ago, some metal shavings got into my top end, destroying the cylinder walls and rings. Full story herehttp://motorbicycling.com/showthread.php?t=50367
Long story short, I got new rings, gaskets, hardware and a cylinder body and put it together. Also have an automotive coil and ngk plug. The cylinder body transfer ports don't match up as well as the stock body and it has a smaller intake. The bike now has runs out of steam around 25. and doesn't run well at all makes strange noises and vibrates a lot more than originally. Could this be the cylinder body or could it be the wrist pin, crank or something worse?

 

[crassius]

got one here like that, factory screw-up on a new motor - transfer ports barely clear the top of piston - cold compression maxes at 125 with high-dome head and doesn't change at all after fitting low-dome head, so it's just unable to breathe

I dug out an old barrel with higher ports and will try it if I get time this week.

I wouldn't worry too much about the smaller intake, but would definitely get a barrel that has same distance from head surface to top of transfer ports.

 

[CranbrookKid]

It's not so much that the ports don't clear the piston, it's their shape. The gasket also obstructs some of the port if that makes any sense. The last picture is the original cylinder body with correctly shaped ports. Is this what is causing it to ride rough?

 

[crassius]

a bit hard to see in pics (some from bottom would be easier). but it sure looks like the shape of the transfer channel is wrong

 

[CranbrookKid]

Yup, that's exactly what I was thinking, I just didn't know the technical term for it. Would that cause problems?

 

[mapbike]

It's not so much that the ports don't clear the piston, it's their shape. The gasket also obstructs some of the port if that makes any sense. The last picture is the original cylinder body with correctly shaped ports. Is this what is causing it to ride rough?

Just wanted to point out that you have the springs wrong on the clutch cable, the big spring goes where you have that thinner spring and the thinner spring goes in the trash.... not useful at all and only makes the clutch harder to pull.

Map

 

[Wickedest1]

Yes the size and shape of ur transfers would def cause more or less vibes...its easy to port those lil cylinders...and cheap to replace if u screw up...id take the chance and try porting...there are some very detailed threads here on how to...but id also pull the top end and check for play in the crank...check ur seals and make sure all bearings are free flowing and mostly silent...u would oklahoma if a bearing is bad by grunge grunge sound...

Portportport

 

[crassius]

I'm thinking your best bet is to go for a new barrel that fits your motor - not sure what you have there, as I've never seen one shaped like yours, but you need a good seal at the bottom and unrestricted flow up thru the whole passageway there.

 

[CranbrookKid]

Thanks for the help Wickedest1 and crassius, I'll hopefully be ordering another cylinder shortly. Good thing I have two cylinder bodies to mess around with (porting etc.). Thanks Mapbike for pointing out the clutch cable issue, I thought I had it wrong but I wasn't sure.

 

[mapbike]

Thanks for the help Wickedest1 and crassius, I'll hopefully be ordering another cylinder shortly. Good thing I have two cylinder bodies to mess around with (porting etc.). Thanks Mapbike for pointing out the clutch cable issue, I thought I had it wrong but I wasn't sure.

Best wishes bro. Hope you have it running like a champ asap.....

Map

 

[mapbike]

By the way looking at that jug it sure looks like one hat I have on my dax, I bought wn engine from LEB a couple yars ago and its still in a box all tore down but it has larger tranfer ports and the intake and the exhaust port was a about 2mm larger also.

Many of the engines I've seen lately seem to have much smaller transfers the LEB engine has, ill look at mine closer in a couple days and see if it hangs over like yours does and report back if it does.

Map

 

[CranbrookKid]

Thanks mapbike, I'm interested to see if I'm not the only one with a strange cylinder body. I've never seen transfer ports shaped the way mine are. Another thing, the bike has a very weird power band. It has good (better than with the orig. jug) acceleration to about 18 mph, then there is a big surge of power to about 25 and after that power drops and it slows down at WOT.

 

[Wickedest1]

jetting the carb will help, plus a pipe, larger carb and jets...bunch of free stuff u can do...buddy of mine used to put about 1/4 of an inch of quicksteel on backs of his clutch pucks to make it grab better...26 inch wheels inflated properly too...dude take pics and make a first time porting thread...lotta in the kno guys here willing to help...

 

[CranbrookKid]

jetting the carb will help, plus a pipe, larger carb and jets...bunch of free stuff u can do...buddy of mine used to put about 1/4 of an inch of quicksteel on backs of his clutch pucks to make it grab better...26 inch wheels inflated properly too...dude take pics and make a first time porting thread...lotta in the kno guys here willing to help...

Before any porting happens I'll prolly need a new jug because I think my ports are a different shape on new jug, so not enough flow. Right now my plan is to get it running correctly. I'd love get a larger carb, pipe etc. but my wallet certainly isn't allowing it.

 

[mapbike]

Before any porting happens I'll prolly need a new jug because I think my ports are a different shape on new jug, so not enough flow. Right now my plan is to get it running correctly. I'd love get a larger carb, pipe etc. but my wallet certainly isn't allowing it.

Sometime tomorrow I will look to see if the jug I have has the same type of look while mounted on my dax lower as your jug looks mounted on your engine.

If they are the larger ports like mine I would get that engine tuned good and keep the jug as long as it works good without any air leaks and makes good power as you have mentioned.

Map

 

[CranbrookKid]

Did you get to check the jug mapbike?

 

[mapbike]

Did you get to check the jug mapbike?

Darn-it ...... got busy with other things, worked on the bike and completely forgot to take pix, I wll definitely get a pic posted tomorrow.... sorry about that!

Map

 

[CranbrookKid]

I've since filed out the transfer ports so there weren't any restrictions and planed the head and the cylinder body. I had to sand down the head quite a bit as you can see from the pics it wasn't completely flat. It raised my compression a little bit and now I've got a much better seal on the head.

 

[CranbrookKid]

I've since filed out the transfer ports so there weren't any restrictions and planed the head and the cylinder body. I had to sand down the head quite a bit as you can see from the pics it wasn't completely flat. It raised my compression a little bit and now I've got a much better seal on the head. I also widened the intake port some.

No I have another headache. The bike runs like crap and has no top end. Once the gas starts running low though, it starts screaming and flies like a bat outta ****. Any ideas on the issue? I've moved the needle from the lowest position to the highest and it made no difference. Could it be that I need a smaller main jet?

 

[mapbike]

I've since filed out the transfer ports so there weren't any restrictions and planed the head and the cylinder body. I had to sand down the head quite a bit as you can see from the pics it wasn't completely flat. It raised my compression a little bit and now I've got a much better seal on the head. I also widened the intake port some.

No I have another headache. The bike runs like crap and has no top end. Once the gas starts running low though, it starts screaming and flies like a bat outta ****. Any ideas on the issue? I've moved the needle from the lowest position to the highest and it made no difference. Could it be that I need a smaller main jet?

Yes most likely your main jet is to big and causing your engine to run way rich, you can resize the jet you already have if you have a propane torch or it can even be done on an electric stove top if done with care and not left on burner to long.

here is a link to the drill bit set and drill pin vice you will need to redrill the jet after the hole in jet has been soldered closed.
http://www.widgetsupply.com/product/WB05.html
http://www.widgetsupply.com/product/SHG3-840.html

I have done many jets using this method, easy, inexpensive and works great, just get a small coil/roll of thin solid core wire solder, with scissors or wire cutters snip off a very small piece of the solder, maybe 1/8" or less, clean jet well with a good spray of carb cleaner to remove the oil, if using a propane torch, hold jet with pliers, lay small piece of solder over hole in jet now heat with torch until solder flows into jets hole and then remove heat and let jet sit and cool for a few minutes, this wont take long. ( its very important not to over heat the jet...!) just enough heat for the solder to flow and fill hole and then no more heat is needed, to much and you can actually melt the jet.

If doing the soldering on an electric cook top, just sit the jet on the heating area put small piece of solder into jet over the hole and now turn the cook top burner on, have pliers near by and as soon as the jet is hot enough for the solder to melt and fill the hole, remove jet and sit aside and turn cook top off.

Redrill with wire gauge bit, the #73 or #72 drill size has always worked just right for my NT carbs.

I hope this will help you.

Map