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[PANDEMIC]

Ok it's me again...on the id tag it says 0.4 - 0.6 for the spark plug gap for a 150cc...is that correct and if not than what is the correct gap...And now for the BIG QUESTION...what is the correct way to break in an engine???? I've heard stop and go then go fast then slow and the one about ride it like u stole it...I'm really looking for the correct or at least the best way.. and one more thing...If anyone out there has a repair manual for the 157qmj if there is a page with all the torque specs could u please slip me a copy of that page

[bull]

Here is a link to a manual which will take care of most of your enquiries.

http://aerox.us/roketa/arrow150_engine_service_manual.pdf

As to breaking in a scooter engine, as you have already discovered there are two schools of thought. Breaking in an engine's primary goal is to seat the rings and reduce blowby. Both of these increase power.

A secondary goal should be to control piston skirt and cylinder wear as it relates to high revving and thrust. Most people fail to consider that these engines revving @ say 7k rpm, the crank is traveling at twice that speed or 14k rpms. To put that into perspective; the crank & piston is cycling at the rate of 233 times PER SECOND!

If you ride it as I do, then you will quickly find that you need to push the engine's limits everyday. However if you do this you need high quality synthetic oil and something in the fuel to lubricate the top side of the piston (not the dome) as that area does not get enough lubrication to protect it. Failure to provide the additional lubricant will yield premature failure.

On the other point of view, you get rings that may never seat (seen that a lot on teardowns) and the engine has excessive blowby and of course lower power. Even in this the top side does not get enough lubricant, but most people don't want to listen to that.

[PANDEMIC]

What would I use in the fuel to lubricate the top end of the piston...I'm not trying to run the hell out of it, that's what I did with the last engine which is why I'm replacing it well that and the original engine came brand new courtesy of a cross threaded spark plug leaving but 2 threads left on the cylinder after the first plug change

[PANDEMIC]

What's the plug gap that manual doesn't say

[kz1000st]

Didn't we go through this already? .027 inch or 0.6858 mm. which is .7 mm.

I'm from the other school. Rings break in with use. On a 150cc I would ride at or below 40 mph with varied throttle. There are other things breaking in besides rings and numerous heat cycles assist with the procedure.

[bull]

Lucas Upper Cylinder Lubricant- added to fuel.

Mobil 1 10w30 protects engines best and provides for less friction.

Plug gap was stated on titled pg 60 / counted pg 64

btw.. "running the hell out of it" is not the problem, it is how you maintain it; plug siezures are typically from lack of antisieze lubricant on the plug or too infrequent changes or cross threading

[bull]

Hey KZ, I've seen and done both ways over the years. Would not care to even guess how many total, but one thing has always bothered me. That is the blowby evidence clearly showing on the piston skirts and how it increased as piston ring tension decreased. Engineering decreased piston ring tension to have engines last longer than 100k miles, many were not even making it to 60k or 70k.

I doubt the ring tension on these engines is even 5psi, and that simply will not seat the rings (removing the cross hatch pattern) good enough in any reasonable amount of driving.

To test my point of view, on the next few builds you do, before tear down check the crankcase pressure @ idle and 5k rpm- I think you will be surprised when you look at the numbers vs blowby residue on the piston.

[PANDEMIC]

Yes kz I believe we did but I forgot and this is the last thing I'm doing to this scooter if this fails than I'm going back to my trucks...I can build a desert racer with no problems but when it comes to an engine the size of a pea it becomes alien to me

[PANDEMIC]

I keep it maintained change the oil and gear oil every 300 miles, check valve gap, inspect variator and roller weights and belt...only thing that I haven't been able to change as regular is the spark plug...I made it through 4 changes before it became serious enough that I put thread lock on the plug for fear of blowing the plug out of its hole

[PANDEMIC]

Ok guys thanks for all the information however I'm still at a loss as to the correct way to break this thing in...I don't need to push it to its limits every day...I deal with a lot of stop and go traffic every day going to and from work but I also only live 15 minutes from work...There are days when I go visit friends and those roads offer higher speeds and less lights so that's when I'll get on it and have some fun...so what would be best and please in scooters for dummies language (I see English but my brain seems to read it in Chinese when dealing with this scooter)

[bull]

Pandemic, we can only share our knowledge and experience. You have to pull the trigger and make the decision.

If you take the time to truly understand these very small powerhouses, you will not only gain respect for them, but be amazed by them. My first engine build was a V8 283CI Chevy. Lots of engine (about 4800cc) but very low in power compared to these little 50cc scooters.

[Irish]

Lucas Upper Cylinder Lubricant- added to fuel.

Mobil 1 10w30 protects engines best and provides for less friction.

Plug gap was stated on titled pg 60 / counted pg 64

btw.. "running the hell out of it" is not the problem, it is how you maintain it; plug siezures are typically from lack of antisieze lubricant on the plug or too infrequent changes or cross threading
I have used antisieze on plugs (motorcycle & any other vehicle ) for as long as I can remember! You can get a can that has a brush fixed to the cap. It almost becomes a habit because it's so easy & it's definitely worth the effort.:tup: Irish