MC 54B 250 Roketa engine redo

[bamaguy]

Anyone on here ever re-one one of these 250's? It's the 250 Yamaha (linhai) clone horizontal water cooled engine. Changed thermostat, heat sensor, wired fan straight, burbed it, checked water pump. Thin now it has a blown head gasket or cracked head or cylinder. At the end there was white smoke coming out the exhaust. Can auto shops check it?
I need any advice on the subject if any mechanics here. I need to know torque settings, timing procedure, ect.
I will post a picture of the head to see if anyone can spot a problem.
It's just like I pulled it off.

alfonzo.pixa.us/images/19348202/engine-head

alfonzo.pixa.us/images/19348242/Head-gasket

Had a charging problem also. Does this stator look like it got hot?
alfonzo.pixa.us/images/19348204/Stator-inside-housing

[noday]

looks like you had a head gasket leak. With just the 1 view of the head, hard to say much else. pics don't always show what you can easily see in person.

You need a shop manual for your engine. Rebel is good at tracking down links for manuals. I'm sure he will give some help.

you really can't tell much from a pic for a stator's function. you need to test it with a volt ohm multimeter. you test the leads for continuity and for shorts to ground. visual usually only shows if something has melted.

stator wire windings have a very thin insulation and can fail and show nothing by visual inspection.

poor battery charging is more often the result of a bad regulator rectifier than the stator. also may be an old battery that will not hold a charge.

here is a link for stator testing... go to the B section

www.chinesescooterreference.com/pdf/Stator_Papers_IV.pdf

[Rebel]

Welcome to the forum.

I emailed you a couple manuals, actually they are forwarded from a friend to me, passing them on to you.

You can also look HERE for a couple manuals.

Since it was over heated you may have warped the head, did you have it checked? Also if it had been leaking for a while the coolant going into areas that it should not go can actually cut grooves in the metal causing it to continue to leak.

If you are not comfortable working on it yourself, I'd think an auto mechanic would be able to take care of the job as long as he has a manual to refer to.

Some of these scooters over heat because of the heat trapped in the CVT, for the future once it is repaired you might look into opening it up to let the heat out.

Possible problem area.




I'd take the head and cylinder to a machine shop and have them check and if needed resurface them.

Since you have taken it this far apart, I'd finish the job if it were me, this is not rocket science. You do have to use a torque wrench when putting it back together and proper sequence when tightening the head bolts. First you snug them down then you torque them.

[Rebel]

If you want to while you have the head off, porting and polishing the intake and exhaust is a good way to get some more power for these.

[noday]

along with what Rebel wrote, I would pull the cylinder case as well & look at the piston, rings and cylinder liner wall. there could well be some ring and cylinder damage too.

probably minor and fixable with a cylinder hone if present.

would also consider a valve job.

since you have the engine broken down this far, it is easy to address these other potential problem areas

another mechanic option is a small engine repair place, (guys who work on riding lawn mowers). they work on engines this size all the time and their rates are usually less than the auto repair guys.

[jmkjr72]

i dont get why they are restricting the water jacket so much with the gasket in those places does the cyl bore have the same sized holes for the water jacket as the head

if so that might expalin why your head gasket came apart there

[bamaguy]

I had the head pressure checked and resurfaced it. They said it was ok. That guy said it looked like a head gasket to him. They do motors for a living. I didn't find just ring set on the site I ordered parts from so I got a ordered new piston and rings. I scotch-brited the top of the cylinder and you cannot feel a ring groove with your fingernail. Not sure the stator is bad but it will have a new one if this one fits. Also ordered a regulator rectifier which are cheap. Didn't want to take that motor back apart if it was the stator. The headlight bulbs very 25 watt and I ordered some 35 watt ones from Bulbtown. Hope it's not too much on the charging system. Just wanted to be able to have useable lights.

Never had this problem finding correct parts for a motor before. Guess because there are so many versions and variations of the same thing. It will all work out.

Thanks for all the help here. If anybody has one of these scooters and needs a picture of something while I have it tore down I'll be glad to takeone. Hard to tell what alls under that palastic till you take it apart.

[Rebel]

Did you check the head for warp-age? I'd hate you to have to take it all apart again because the head warped after getting too hot.