non-Penton tech help request

[OhioTed]

Hey, guys - I hate to inquire on the POG site about bikes other than Pentons, but you all have so much cumulative knowledge that I'm sure someone can comment on this:

I am working on a '66 Honda Super Cub.  Well-preserved example.  Sat for years.  All intact, just needing awakened.  I rebuilt the top end, including new valves, piston, rings, bore job.  Carb was soaked in dip tank, then passages blown out.  All jets look good.  Note, no attention to ignition system, as there is plenty of spark.  

Bike now starts right up, idles fine, and will pull full revs on the stand.  However, it will not pull any load.  Even under partial throttle, in gear, with rider aboard, engine spits, rattles, and pops back through the carb.  

I had the carb back apart this last weekend, cleaned it again, and can't seem to find any problem with fuel flow.  That leaves ignition.  Like I said, I didn't touch it.  Could this be weak coil/condensor?  What about advance?  I don't have a battery in the bike yet.  Could that make a difference?  I just don't understand how it can rev to redline on the stand, in gear, turning the rear wheel, yet will not even run under any kind of load.  Suggestions?

[Randy Kirkbride]

Ted,
Anyway to check timing??

[454MRW]

How about adequate valve lash?
Also make sure the petcock on the tank flows unrestricted fuel. I had a problem with a 76 XL175 Honda that would run out of power and quit and I thought it was an ignition problem, but it turned out to be a overly restrictive petcock. It seemed to flow fuel fine, but when the level in the tank got a little low, the gravity didn't create enough fuel flow to properly fill the float bowl. That one took a while to figure out. Opening up the passage further in the petcock cured the problem. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[sixdazed]

Ted,What is the model designation(c100,102,etc.)?If it's a 66 that should be the first year ohc model.If so-is the cam timing correct?If i remember right it has a circle(or line,dot)on the cam sprocket that lines up with a notch on the head with piston at top dead center.If it's a pushrod model disregard what i just said!Also you might try running it partial to fully choked to see if it runs better or worse-if it run better with choke you have a lean condition,if it runs worse then it's rich.Make sure the needle in the carb slide has it's clip and the retainer on top of it,and while squirting carb spray thru pilot circuit with pilot jet and adjustment screw out a small strean should come out where lo speed air/fuel adjustment screw is and air bleed tiny hole in venturi.The emulsion tubes tiny holes(in the main jet holder)also need to be clear.Points should be gapped at .012-.015 thousands and just start to open when the f mark on the flywheel lines up with mark on case.A yellow spark usually means a bad condensor-it should be nice and blue.Hope this helps-if you give us the model that may help with other ideas.
                                                              Ric

ric emmal

[firstturn]

Everything Ric says is spot on (It should be he is a Honda Registered Tech which is no easy feat).  One other thing I would try and this can be testing the valves and the rings is what is the compression.  And as Ric says which model is it?

Ron Carbaugh

[OhioTed]

The bike's owner tells me it's a '66, but it still has pushrods.  It's a 102 (with electric start).  This last time I had the carb apart I cracked open the petcock to the float bowl.  Appeared to be plenty of fuel flow.  Especially after this last carb cleaning I am pretty confident that all the passages are open.  

I must admit that I have done very little to the electrical system.  Static timing, point gap, and all components are (probably) original.  

I set the valves after rebuild, but what is valve "lash"?

A weak condensor could be the problem, if indeed that would account for the bike revving well on the stand but not under load.  The bike has decent spark, but I could not say if it is blue.  

The bike starts first kick, every time.  Any factor there, relative to weak ignition, ie: the aformentioned condensor?

[sixdazed]

The compression check is a good idea-even on a fresh rebuild-Thanks Brother Ron!I thought of 1 more thing-is your air filter in place and is it clean?what does the spark plug look like when you remove it?-maybe the plug reading will give you a hint.
                                                       Ric

ric emmal

[454MRW]

Valve lash is the amount of clearance between the end of the intake or exhaust valve and the rocker arm or push rod that allows for expansion created by heat generated once the engine fully warms up. Not being familiar with the specifics of a 66 Super Cub, I am not sure how this applies, but most pre-80's 4 strokes have adjustable valve lash and if either or both of the valves are too tight the engine will not run right and pressure and/or vacuum loss at the valves will occur. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[tomale]

I know very little about Honda's but I had a thought, how about the exaust pipe. has it been checked to make sure it is free of debis.. I had a bike would not turn over, I was pretty sure the top end had rusted tight. AS it turned out was a mouse had crawled into the cylinder just below the piston. with all of the bedding it created such a mess.. So I thought it would not be beyond the possiblity for something to have crawled into the pipe... not worth much, just a thought.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[firstturn]

Thom is correct as I always try and separate the pipe form the issue.  I have seen some of the best fooled this especially on 2 strokes (I know this is a 4 stroke).

Ron Carbaugh

[t20sl]

Ted:
   First, C100, CA100, CA102, C105T all were pushrod engines all years. Cam timing would not be issue unless you had bottom end apart.  Word of warning to all Honda owners is Honda used plastic (nylon) guides to keep slide from turning in carb bore on many early models.  NO DUNKING in carb cleaner.  I have seen this destroy the plastic and let slide rotate causing some real erratic behavior.  Probably not the case here.
   Did you check each jet by holding up to a light source?
   Before trying new points, condenser etc, clean points with 500 wet or dry sandpaper.  Just cut narrow strips and pull thru several times using the points own spring pressure.  Face sandpaper one direction then the other.  When done manually open points and clean with contact cleaner to remove sanding dust.  I always try this first going on assumption that it ran with timing the way it was set at one time.  Of course we all know what ASSUME means.  You will need a flywheel puller to put in new points but not cleaning them.
   Also take off spark plug cap, snip off about 1/8" to 3/16" of wire as long as you have any extra.  Shake cap and listen for any rattles.  Some had a resistor in them and sometimes goes bad.  Check cap with ohm meter.  No resistor one should be 0-2 ohms.  Resistor should be 5000 ohms.  If higher put new cap on.  No resistor is needed unless you plan on listening to your radio while riding.
Ted Atkinson

[tofriedel]

In terms of spark color, this is what I have used forever -
White is right, Blue will do, Red is dead.

It has always worked for me.

Tony