Low compression - Honda CB200

[Roger Reynolds]

Hi all,

 

I've been struggling with the carb adjustment on my CB200, and not making any progress even after doing a couple of carb rebuilds and attempting to perform the carb adjustment procedure several times.  It barely runs at all now.

 

I measured the compression today, and am getting 100psi (cold) on each side.  Pouring a little oil into the cylinder gets that pressure up to 120psi.  The bike only has 4k miles on it, and I did have it running well enough, a couple of months ago, to put about 70 miles on it and it would run up to about 70mph.  I bought this bike to ride it to have a little commuter to ride to work during the nice days, but it's just turning into something I work on and get nothing out of.

 

Roger

[Trey Mitchell]

Someone more knowlegable than me will hopefully speak up, but my understanding is that if compression increases significantly when you put a little oil in like you did then that mean either the cylinder, piston or rings are worn. I'd guess the problem is your rings.
 
4k miles isn't the problem, it's the 30+ years. I know I was amazed when I traveled down this vintage motorcycle rabitt hole to learn that internal engine components will wear even if the bike sits. Time takes us all eventually I guess. If I sat  on the couch for 80 years I'd probably not prolong my life and I guess the same is true of engines.
 
Guys, Is 100psi on deaths door or might Roger get a little more out of this bike before tearing into the engine?
 
Roger, what are the symptoms you are trying to address?
 
-Trey 

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Date: Sun, 17 Jun 2012 12:36:57 -0400
Subject: Low compression - Honda CB200
From: roger...@gmail.com
To: vjm-owners-of-c...@googlegroups.com

[eod...@hughes.net]

100 psi on the old stuff is not the death sentence.;  Especially if taken cold.  Run her a while to normal operating temp and try the PSI again.  The typical rule of thumb is that if oil helps bump up the readings, then rings are needed, however, with age comes “sluggishness”.  You may find that running her a few times may loosen up a frozen ring.  run a tank full with Teckron/SeaFoam, etc, to see if that helps. 

 

The good news is that both sides are about the same, which tells me it is not a burnt valve, etc.  However, with this all said, if the rings are surely stuck, then the only recourse may be an upper end inspection. 

 

ENSURE the timing is spot on... it may have nothing to do with the carbs.  You would be amazed on how many of these old bikes poor running was a simple points setting... the rule of thumb is 10 degree before TDC unless the manual states otherwise...  Also ensure the air cleaner is clear... any reduced air flow will impact response. 

 

good luck... \

kelly   

 

From: Roger Reynolds

Sent: Sunday, June 17, 2012 12:36 PM

To: vjm-owners-of-c...@googlegroups.com

Subject: Low compression - Honda CB200

 

[Bee Johnson]

At a shop the first step was to compression check, 100psi was the magic #, any less and we called the owner before work would start.

 

[Roger Reynolds]

Thanks everyone.

 

So, with only 4k miles, it seems to me like the rings can't be worn out, but must be stuck / gummed-up?  If so, is there a way to try to free them up, or will I need to just go ahead and do a top end re-build?

 

I've double-checked the timing and air cleaners.  Just can't seem to get the carbs adjusted so it will idle and run properly.  The plugs keep fouling after only a few minutes (or less) and stop firing.  If I pull them out and burm off the fuel with a lighter then wipe them off, it will fire right up again, but not run for long at all.  Would the low compression be making it impossible to adjust the carbs, or is it more likely that I just don't know what I'm doing?

 

Thanks,

Roger 

[John Peterson]

I don't think it's compression - your compression test for Both pistons should read about the same for each, which you say it is...and a 200 isn't going to throw that much compression anyway - I'm assuming you tried adjusting the mixture control screws in the carbs, that control the air/fuel mix??    If your plugs keep fouling, you're running rich, obviously...are the plugs the right heat range for that bike? It sound like you need to get more air in there to lean out the mixture...do you say you have a manual...? --- On Mon, 6/18/12, Roger Reynolds <roger...@gmail.com> wrote:

[Roger Reynolds]

Yes, I've been following the carb adjustment procedure in the Clymer manual for my bike, but have been unable to get the carbs adjusted so it will idle and run properly.  I've disassembled, cleaned, and rebuilt the carbs twice; the second time with new jets, valves, adjustment screws, etc.  Have checked / set the timing and attempted the carb adjustment several times, but have never gotten it to idle.

 

I've been rebuilding the carb, and tuning my '66 Beetle for almost 25 years.  I must be missing something, but can't figure out what.

 

Plugs are new, and I have - what looks like - the original plugs that came with the bike.  The "old" plugs look good, but re-installing them didn't improve things.

 

Thanks,

Roger

[John Peterson]

Hmmm...is it Missing anything, like an o-ring on the adjustment needles or anything...?   Vacuum leak? Could the butterflies be out of adjustment...?   This is what I HATE about carbs...adjusting them without having a motorcycle mechanics degree is a Dark Art....

[Bee Johnson]

The other possible issue is the 30+ year old electronics. coil's get tired, and weak spark causes fouled plugs.

[Roger Reynolds]

The spark - when the plugs were clean - looked strong to me.  Not tired and yellow, but nice and blue-ish and bright.

 

Roger

[Trey Mitchell]

Roger,
 
Sorry if we're asking you to repeat yourself, but remind me what you've got for air intake? Is it the stock air box and filter or something modified? Is it a new filter?
 
-Trey
 

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Date: Mon, 18 Jun 2012 17:45:17 -0400

Subject: Re: Low compression - Honda CB200

From: roger...@gmail.com
To: vjm-owners-of-c...@googlegroups.com

[Roger Reynolds]

I have the stock air filters.  They're not new, but seem to be clean and in good condition.

 

Thanks,

Roger

[Trey Mitchell]

Roger,
 
And you're sure you've got the right jet sizes for the pilots? I'm grasping at straws here, but I'd try new air filters. You're running way rich, the filters could be part of the problem even if they look OK. Can you start the bike and then pull the filters? Maybe see if it runs longer that way.
 
You've tried everything else right? If 100psi isn't a death sentence then it's worth figuring this one out.
 
Speaking of everything else... You've set the float levels with the clear tube method right?
 
-Trey

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Date: Mon, 18 Jun 2012 19:42:34 -0400

[Roger Reynolds]

I'll get back out in the garage this weekend and make sure that I check / re-check everything that folks have suggested, and send out a note about what I've found out.

 

Thanks everyone for the advice.