Troubleshooting the cb200

[LaCucaracha]

Woot woot, another new member problem. I have been a lurker here for some time now; awesome site. I picked up a '74 cb200 last week on the list for 350. From the looks of it it looked in pretty nice clean condition. It appeared to need only a carb cleaning, valves, timing, a battery etc. to get it up a running. It now has compression, spark (maybe a bit weak), clean carbs, rust free tank, valves adjusted, timing set and a battery hooked up. I hit the starter button and got nothing, not even a cough. I took out the plugs and they were dry. I figured this was probably a carb problem, no big deal. I checked them, they weren't the problem. I cranked the engine again, same thing. Plugs were as dry as a bone. I took off the airfilters (who knows why) and noticed when I cranked the engine it seemed as if the gas/air mixture shot backward, toward the back of the bike. I am not sure if this is normal when the airbox is removed. But anywho, it led me to assume the carbs weren't the problem. It is almost as if there is back pressure and the gas/air mixture from the carbs gets blown backward, away from the engine. The guy I bought if from said the usual 'it ran last year before I put it away.' Who knows maybe it did. Could it be that the previous owner assembled the engine improperly? I have very little experience with the internals of engines. Any ideas?
Thanks a bundle!

 

[kagraves]

I am newer to this but ill try and help. Sounds like the intake valves are not shutting or not at the correct time. Thus sucking gas in on downstroke and throwing it back up and out the intake valves on the upstroke. Or it could be set 180 degrees off and sucking in through exhaust and out the intake going through the carbs taking gas with the air. I would recheck your gaps and make sure they are at the correct crank positions. When setup correct it should never send gas backwards.

Hope this helps

 

[frogman]

How are you sure its not the carbs if the plugs are DRY? Put your hand over the intake on the carb and spin the engine over, it should pull fuel out of the carbs, might get some on your hand. Coughing back through the carbs is possibly just the engine running backwards for partial turn once you let go of the button, Happens. If you have leaky valves this will also happen, not good.

How much compression? Tested with a gauge not your finger.

Timing is set dead on, according to your manual? Is the advance unit put together correctly and working?

Have you checked and set valve clearance according to your manual?

Is the wiring from your points to your coils correct and connected to correct side?

GOOD fresh oil? Not fuel fouled 30 year old crap?

Best advice, NEVER believe PO's, no matter what they say. However, there is no reason to worry about internals unless you hear weird noises or the engine locks up for no reason.

 

[LaCucaracha]

Thanks guys for the replies. I set everything just as the manual says multiple times. I took your advice anyway and adjusted the valves for the fifth time, but this time I made sure I was not leaving the valves too loose. I set the timing: it was only slightly off after the valves adjustment. I do not have a compression gauge right off hand, but I was planning on picking one up today if I couldn't get it started this morning. I cranked the engine and . . . nothing. Right about this time I was quite frustrated and on the verge of crazed. I got the hairbrained idea of bump starting it. It was quite a sight, no tank, or seat and a battery bungy corded to the top of the frame running barefoot down the street:
http://www.youtube.com/watch?v=OkzmOy9_F04
(sorry there is no documentation of the growl, but the camera battery died right at boom time)
That old bike must have felt sorry for me because she fire up. I believe your first suggestion frogman could have solved my problems. I found out after riding down the street that it was leaking oil out of the 'right cylinder head gasket' between the points container and the engine head. My newbie-ish guess is that the compression is too low and it needed a little more force then the kick starter or electric start could give. But then again, maybe that explanation just shows my stupidity. Anywho, I give my heartiest thanks to you both, frogman and kagraves. Hopefully I can pop a gasket in there and she will run like a champ.
Thanks again!

 

[Bert Jan]

haha nice movie of the bike not running...

 

[kagraves]

Have you had more fuel spitting out when trying to start the bike? Glad to hear you got it going thoigh

 

[LaCucaracha]

haha nice movie of the bike not running...

I was just checking to see if you guys were paying attention.

Have you had more fuel spitting out when trying to start the bike? Glad to hear you got it going thoigh

The gas doesn't spit back when I bump start it or when it is running, just when I am cranking the starter or kicking it.

Here is the deal. It will not start with the electric start or by kicking. This is the process I have to go through to get it going. I run it down the street pop the clutch and keep pushing to bike while I twist the throttle in small increments until the engine sounds like it is running roughly. I can then hop on the bike but then I have to pull the clutch and rev the engine high then it begins to sound and run more smoothly. It still will not idle. I realized this could be a whole bunch load of things since the pipes have rather large rust holes in them, the intake is not stock and one of the sparkplug wires was pieced together by the previous owner. (is it true that the only way to replace the wires is by replacing the coil with another cb200 coil?) While these I assume are a contributing factor, I don't exactly believe they are what is stopping it from starting easily. The top end is leaking some oil from beneath the valve caps/ points cover height. Could this be the problem? Could this be checked with a compression gauge?

I am going to make it into a cafe racer, so now the back end is stripped down and I am working on the electronics tray and seat. My original plan was to finish the bike sans the paint job before I head off to my freshman year of college almost 700 miles away. I won't be back to work on it till thanksgiving. I have a week left, and things are getting slightly hectic getting 'college stuff.'

Anywho, here is a little teaser. I wanted a tan or brown leather for the seat, but that doesn't go so well with the black tank stripe, so my brother made me a pretty slick leather one:
http://roughewn.tumblr.com/post/57198518610
I will keep you posted on further progress, maybe I will start a build thread. Thanks for the help.

 

[frogman]

A low compression engine will take forever to get running, not idle once it does, and will not have any power. I can state this from experience, I used to have a CT-70 that we had to PULL start down the road for around 100 yards before it would WARM UP enough to run somewhat. It never had any power and never would start easily.

I tore it down one winter, honed the cylinder, put new rings in, and lapped the valves and put it back together. It FIRED and ran, COLD as it was, on the 3rd kick. Was never able to kick start that thing or trust it. After that it went everywhere with me, was just the perfect size for a haul around bike.

Now you could have your timing set WAY TOO advanced, meaning that it will only run once you have that engine SPUN UP fast enough.

And yes the only way to replace a wire is to use new OEM coils or use suitable replacements and wires. I don't own a 200, but I believe they are different then say a 350-360. Might just be running on one cylinder.

Get a compression tester and see what it does, needs to be above 150 each side, more like 170.

 

[Bert Jan]

gas spitting back is not good, but not really bad either. I've had that on a 200. Usually means bike is set WAY rich. I have 85 mains and pods on my gf's 200 and it runs strong.

The symptoms you are telling lead to assume compression is very low, so yeah, get a compression tester and check. Do it at WOT and crank her like 5/6 times until the meter does not go up anymore. Anything under 130 is bad news. 150 is ok, 170 is perfect.