Motorcycle Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hope someone can help me. Son's 87 Honda (that double carb thing) starts fine hot or cold. Poops around town fine, Idles fine. But when you get out and start pushing it.. all of a sudden it goes super rich (I think) and starts to bogg badly. Acts like you just added the enricher (choke). We even tied the enricher closed in case it was opening by vibration. Let it cool off and runs great again. I thought about manifold leaking but that would cause lean condition not rich. It does have some oil showing around cylinder head.
I think its the valve cover gasket not head gasket.

Do I have a needle and seat sticking ? Do I have a coil breaking down when hot? I ride a Goldwing.. and it just runs and runs. This one has got me going. I might add I have not had this happen to me. So going out today to see if I can make it happen (and run some sea foam through the fuel system at the same time) By the way when running as it should.. hard to believe it's only a 250. The old man can't hold it open very long.

thanks for any suggestions.
dm
 

·
Registered
Joined
·
121 Posts
First step might be to confirm the problem is running rich as opposed to lean or a spark problem, or (hopefully not) a seizing engine. At full throttle the richener will not do much since it only adds to the pilot circuit. But when the bike is bogging you might pull on the richener and see if the problem seems to change at all. If so that might confirm a rich condition. But it's hard to figure what could cause over-rich only when hot.

Lean running or fuel starvation might be more likely. Clogged petcock screen, clogged gas cap vent hole, etc. Open the float bowl drains and catch the gas in a can and make sure flow is strong and continuous.

Did the problem start suddenly? If so did it coincide with any modifications or event?

A bad coil or CDI unit are possibilities. If you have a friend with the same bike the easiest test is to swap parts. Otherwise a shop can test the coil but the only test for most CDI units is swapping with a known good part. Good luck,
-Bill
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
Thankyou Spurlock. Just got back from 35 mile test ride. It is not heat related and it is not running rich. (Wish I could change the title of this thread)

Here is what it did. Started fine.. About two blocks from home... I could tell it was not running very smooth. No change after it warmed up. 45 miles per hour with my 200 lbs was all it would do. Held it that way for about 5 minutes and it took off.
If it was a twin I would swear the other cylinder came on line. All was well during my test ride.. except for one time... the power dropped off again for about two blocks.. then came back and ok for 25 plus miles. Never smelled gas.. don't think its running rich after all. Vapor lock? Doubt it as it was doing it after only 10 minutes.

My first thought was bad coil... but then maybe it's the Sea Foam doing it thing which of course means carbs. Valves got pretty noisy I will have to attend to that.

Now with this new information... Your thoughts.
 

·
Registered
Joined
·
121 Posts
Hmmm . . . those intermittent problems are tough. Definitely check that fuel is running freely into both carbs by opening the float bowl drains. It's possible one float or float valve is hanging up at times.

I'm suspecting an ignition problem though. Several possible problem spots there: bad windings in the stator coil causing intermittent loss of adequate power to the CDI module, ditto for ignition coil (but coil problems usually get worse with heat), bad exciter coil, bad CDI module, or intermittent poor connections in the wiring harness ignition circuits.

An easy place to start would be cleaning/tightening all the connectors. Next get a shop manual and check resistance in the stator ignition windings, the exciter coil, and ignition coil primary and secondary windings. Unfortunately that is not a sure fire test if there is a partially broken winding that is intermittent. The CDI modules sometimes develop bad solder joints inside which can cause intermittent symptoms. The CDI is discontinued by Honda but may be available from aftermarket suppliers. As I said above, the best test is just to swap it for a known good unit. It is possible to repair them sometimes if the problem is bad solder joints. I repaired mine and wrote it up here: CDI module repair

And of course you should replace the spark plug just to eliminate that possibility. Good luck,
-Bill
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #6 ·
Adjusted the lifters today.. they were a little loose but better than too tight.
While the tank was off I took all the modules off and cleaned them up paying special attention to connectors. Back together and no real change.
Spurlock I was very interested in your cdi repair. If I nail it down to the cdi... I will try that.

I found a post over on vintage Thumper bikes with the same problem. The stator, the cdi, the pickup coil and the sticky float needle were all mentioned as the solution. We will let it simmer for a bit and keep trying.

Thanks
dm
 
1 - 6 of 6 Posts
Top