New to motorcycles trying to learn

The Basics:
Compression: When the engine runs you have compression.
1. This is the first move so you don't buy a head. WOT are the compression numbers?
2. Might start at 100 psi, but that is not the factory running number. Low range or 1 number below the low running compression number is time to rebuild.
3. Engine starts, it's a sign that you have compression without the test.

Fuel: When the engine won't start, this is 1 of 3 variable to running.
1. The flow chart is gas cap vent, hose kinked, or imploded separation inside the line, stuck float, stuck float needle, no gas in tank, petcock does not flow.
2. Adjustments out of spec at the air screw, slide in backwards, float bowl out of range.
3. Dirty or clogged jets, dirty air cleaner element to cause a rich condition. So hard starting, no idle, poor gas mileage.

Spark: When fuel and compression are there, this is the last loop of the running of any engine to a BBQ pit is how an engine/charcoal fires off.
1. The points stay closed when the engine rotates.
2. The coil is not receiving 12v to the coil.
3. The coil itself is burnt internally.

The 3 basics have almost an endless variable to each of itself. That takes basic knowledge to know your 3amigos and who is the bandit of the 3 so as not to start.

So the engine running shows compression. The spark is there keep the engine running. Fuel is there to keep it from stalling. Memorize the 3amigos and you are on your way to walk up to any bike and know which is not in play.

Look in each carb and see if the slides are reversed backwards. There is a line machined at the slide and a guide pin pressed in the carb body. New cables installed? Has to be a slide stuck open to raise the rpm.

You're first move is to check compression so you more have a parts bike if parts are no longer available. But if you got it running, it shows compression. So first check oil level height, so you know 'splash lube' can fling up the cylinder walls and lube a cold high revving engine. The quick turnoff won't heat and expand the pistons to stick to the wall.

So as to make sure that didn't occur, you can smell the burnt oil. That would be neck snapping back, a metallic cooked aluminum smell. The other would be a gas smell and the oil would fall off like water. Last smell is an oil can smell mixed with exhaust fumes and the oil looks gold in color.

Keep the engine together so as to diagnose the PO's observation. Base gasket blown out or corrosion just from sitting does not show a continuous leak per say, or the bolt head would not be that rusty. In other words it looks dry.

Move to the carb slides for now. Bike shows all 3amigos so think about it why the head buy?

Oh dear.....

Get a manual...you know of CMSNL.com for the informative exploded views...

Oh dear, sealer on cylinder base and between cylinders at the front is not a good sign !

If you can source a kick start version of this engine, brilliant !



Please remove cam cover, 2 chromed bolts and large cupped washers...if your fighting it your doing it wrong. Post several pictures of cam/valves ( 6 valves in total ? ) Area from both sides...

Do your research, look at engine exploded views on CMSNL before it does....post those pictures.

The positive side I'm looking at, its a frame with a title, if nothing else I have a rolling chasis lol. I haven't started removing cam cover yet, that'll be a day or 2, I'm working on getting some of the sealer off before I open it up cause I don't want it to all end up in the bottom of the engine, it had same stuff on the carbs by the rubber and on cylinder head same place, looks like there was a hack job on the wiring too, I'll have to take pictures tomorrow once gets daylight ish, I got about half the sealer scraped off the bottom of the jugs, it was all the way around.

I have the clymer manual for it, the only thing that's shown up in a timely manner, I will look at the link in a few gotta get tools up before it gets darker.

What engine is it with the Kickstart, would it be the 400? And is it a direct bolt up or would their be modifications needed, Kickstart would kinda be a good plan. Since I was having to rollstart my shadow this morning cause the battery died.

Thanks for the tips and advice

Hi Vernon,

Some car experience...

Not many cm's made it to the UK.

This is a good bike to learn stuff on, it will be an enjoyable/frustrating experience as "JB weld" is evident.

Any signs of sealer on the crank case's horizontal joint at all ?

Pictures pictures pictures.

It's good you have a book and now know of CMSNL.com.

Suss out why cylinder base sealer "is not a good sign".

Pictures of cam area to establish a few things...and carbs problem.

If you intend an engine strip down, you will need a clutch nut "spanner/socket" ( there is a how to make one thread on here ) and a flywheel extractor bolt, same size and thread as oil filter bolt for reference.

I assume you have needed tools and know how to get stubburn nuts, bolts and screws out.

Do not strip down engine yet, apart from cam cover for pictures.

Balance chain adjustment and "dot" ?

Dot just about visible via that slotted round cover plug...

Do your research, study manual and CMSNL views, time well spent.

Feedback as it's polite and helps others.

Take your time, enjoy.

Ps, cb250n, cb400n kick starter parts might, as in "might" fit cm's, but they are sought after parts.
Enguire...

More "clear" pictures hopefully.

The spare engine will be of use, stuck pistons can be free/removed but that's for later.

Use the spare engine to suss out balance shaft DOT...

Likewise cylinder base gasket...

Is the cylinder off the spare engine ?

Research cylinder head bolts...the first picture suggests that left front outer head bolt is "incorrect", meaning other will be also. DO NOT, that is DO NOT screw in any head bolts untill you know 100 percent they are in the correct holes !!!!!

Missing c/case bolts, that "depression" ion in cam cover head sealing face, the cam cover bolt and that spark plug all suggest problems...

More clear pictures...

Spare engine, bent valves, cam chain Broken, valve guides broken ????

This bike will be quite a steep learning curve I think, but you have a "safety rope".

Study manual and CMSNL views...

Compare engine numbers and CMSNL info...

Hi Vernon,

Seems this bike has had an "interesting" past.

If you intend to strip this engine down; which sounds highly likely; you know you will need a flywheel puller bolt and clutch nut peg spanner.

As you know, to completely strip the unit down, you will have to remove it from the frame.

Before you remove it from the frame, it is wise to loosen certain engine internal bolts and nuts.

Flywheel bolt, crank bolt on clutch side and clutch nut. The bike has mechanisms to stop parts from turning so these nuts and bolts can be loosened with the engine in the frame ( but an assistant needed ) rather than struggling to loosen said fasteners "on the bench".

Spark plug hole " helicoiled/timeserted" or made oversize, d sized plugs are standard, b size plugs are not.

You may need a "plug tap" ( finishing size ) for the cylinder head bolt holes in the crank case, 10mm X 1.25 pitch from memory.

I have come across many ruined crank case uppers with half missing ( burst ) cylinder head bolt holes, the 4 inner bolt holes, caused by incorrect bolts fitted and sealer causing the holes to burst.

Access the spare engine to see what you have.

Even if your not a church goer, several " please god's" and "thank you god's" may help, but you may already know this from your car experience and knowledge.

Take your time, be methodical, get some boxes but most of all, enjoy.

You have good JIS screwdrivers and bits ?

Keep giving feedback and pictures as it helps others and you.

I am in the process of making a list of tools i still need to procure, so far that consists of valve compressor, flywheel removal bolt, jis screwdrivers and chain breaker.
I'm sure the list will grow as it goes along but with bike being total learning experience only so much help online research can do in preparing

Since the parts motor was half stripped when I got it. I removed and started cleaning the parts up, to see what can be reused if needed cylinder head, after soaking in atf overnight and about 3/4 hours brushing It, is almost usable.

The 4 center head bolts have been snapped, I'm guessing they didn't soak it before they tried to remove them.

The starter from the parts motor still needs some more cleaning but I have it where it spins freely again.

The stator and flywheel are ruint on parts motor as the flywheel appears to be stuck on it and someone tried to remove with a hammer.

The cylinder jug unless I can find new sleeves for it, won't clean up enough to reuse.

Its missing clutch pressure plate I think it's called. Along with other pieces from under the side cover as when I removed the bolts holding it on there were several springs and stuff that fell out.

The crankcase has couple of chunks broken off towards the bottom of it.

There are no pictures from the clean up process of old parts motor, just bunch of parts piled up in the passenger seat of the truck along with couple plastic bowls that hold the reusable bolts.

Thanks for the advice,
Is there anywhere specific, you would recommend for jis screwdrivers and the other tools needed or just anywhere online?