On Tue, 6 Jan 2009 02:49:33 -0800 (PST), wrote:

On Jan 5, 7:31 pm, Gunner Asch wrote:
Ive been trying to get that '74 Honda XL 350 to run properly...with no
luck.

Pulled the carby tonight checked everything, Replaced idle jet seals,
made sure float was at proper height.

Timed it, adjusted valves, point gap..the whole encilada.

Will idle just fine Coughs and runs ragged and will stall if adding
throtle. The idle screw seems to do very lttle if anything. Bike seems
to not care if choke is on or off.


Gunner, your thinking like a Company Engineer with access to unlimited
tools and free parts from the company store room - stop it! - you will
be ruined for civilised company.....start thinking like the
resourceful rat engineer we all know you are....

LOL

A few points, from this and previous postings...

have you checked there is fuel flow (ie, more than a leak) from the
tank? - if its been sitting for years, God knows what sediment / muck
is clogging the gauze filter at the bottom of the fuel taps. (or,
indeed, the fuel line to the carb)

Yep, cleaned the tank, pulled the petcock, cleaned the sediment bowl
anhd filter, added a decent new inline filter and new hoses

Have you checked the exhaust port, even visually - is it carboned up?
- ( you said it was blowing smoke anyway) have you checked the exhaust
pipe and muffler, with an air line or a piece of stiff wire as a pull
through - maybe something has crawled in there and died?

No, havent done that. Its a good idea however. I do have a reasonable
output of exhaust from the spark arrester. But I will check that.

Finally - the ignition system. You say you got a 6v coil and condenser
from an old truck - how old - must be eons, 6v systems went out in the
50's. How do you know the coil is good - obviously it fires, but what
happens when its loaded up, ie you open the throttle. I suggest you
temporary wire up a known good 12v one from an external car battery,
see what happens. You can then use your timing light to see if the
advance/retard thingy is working. And BTW - a 50yo condenser is likely
to be crook as well, either leave it out for the moment, or get a
known good one.

I got a good used Motorcycle coil from a parts bike similar to mine. 6vt
AC (ac magnito ignition) and a brand new condenser from the autoparts
store. Puts out a decent blue spark now. Also a new NGK plug and NGK
plug cap on the end of the spark plug wire.

It comes down to carburetion or ignition - the ignition is the easiest
to prove. If it passes, then look at the carby suggestions others have
posted here.

The bike sits and idles well enough. It just turns to **** when tweeking
the throttle. I need to find another carby. I carefully cleaned this
one, using mig wire on the small passages, lots and lots of compressed
air and a soaking in Berrymans Chemtool carby cleaner. I replaced all
the seals with brand new o-rings, and made sure the crush fit didnt
close any of them off. The original seals being flat rubber disks with
a hole in the middle between the various bits. Replaced idle jet seal
as well.
I really need to find another carby, even a loaner to test with. This
one may be utterly stuffed. The odometer had 17,000 miles showing,
which while not a lot...is significant.

And it will be a nice hooning around bike at the end of it - don't
worry about the camshaft bearings for the moment, it will/should run
reasonably even with stuffed ones. Spend big bucks when everything
else is proved.

Im sure this bike has two problems,...the carby..and the worn out cam
journal (s).

The way Honda does it on most of thes bikes...the head has half of of
the cam journal machined into it, a cradle the camshaft lays in...and
there is a cover that goes on top of the head. It has ports to adjust
the valves and so forth. The bottom of the cover has the upper half of
the camshaft journal machined into it No journal "caps"...they are
machind into the cover.

When I turn the engine, so all the valves are closed and the pressure is
off of the tappets, I can move the end of the camshaft that carries the
points cam a significant amount.Probably 1/8" of an inch...3mm? in the
horizontal direction side to side, and a bit less up and down. This
movemen is affecting the amount and time the points open and close.
This also effecs if the valves open, how much, and when. Double
overhead cam...two exhaust valves,, two intake valves, single cyllinder.

Hope this helps, all recollections from when I was a penniless bum and
had to keep my bike gong.....

Andrew VK3BFA.

The bike starts hard, unless I use an oiler and spritz some raw gas into
the carby, past the slide into the engine. Then it starts fine,

Ive played with the timing, with the engine running,and found the sweet
spot where it idles fine, but it still wont do anything other than bog
when I tweek the throttle. If I creep up on it..after about half
throttle, the bike will suddenly speed up normally to high rpms.
Normally Id think this was a carby issue...but watching the points cam
shaft wallowing around like a drunken sailor..I think that at the higher
rpms, the end of the cam shaft is now spinning fast enough to get some
gyroscopic stability and enough oil is being pumped into the worn out
journal to pile up in it and get a thick film around it which helps
stabilize it when its spinning., and this now allows the cam to run
fairly true..concentric and the points are opening closing in a
consistant manner.

Ive ordered a proper carb seal kit from Ebay and when it arrives, Ill
install it. But..the carby may simply be worn out, thought the slide
appears smooth, and slides smoothly in the slide bore. Needle jet is in
the proper clip setting according all the online sites devoted to this
bike.its quite a popular bike for flat tracking, etc etc. Which makes
finding cheap parts a bit more problematic...what the market will
bear....

A fellow down south mentioned that he has a Mikuni 38mm carby..which is
one of the ones easily adapted to this bike, but Ill have to install the
proper jets and so forth.

The California bike boneyards want huge money for used parts, so unless
I can find a head on Ebay...and know it too isnt worn out. and a
carby..same concern...I have to work with what I have.

Chucle..if I was over engineering..Id have ordered a new head $485, a
new head coverr $135, a new carby $350, and a new camshaft $215.

Or send in the head/cover to one of the bike racing shops for a line
bore $150, and a new cam with needle bearings $350....

Instead ..Im probaly going to bolt the head and cover to an angle plate,
and carefuly bore out the worn out journals to fit bronze bushings,
clean up the camshaft if possible, or grind it clean, fit the bronze
bushings to it and the bored journals and see if that fixes it.
Having that camshaft bounching around inside of that aluminum journal
cant be doing the journal any good..it can only get more and more hogged
out and its likely to be doing the far side journal damage as well.

Boring this is going to be interesting..as the inside journal is
significantly bigger in diameter than the outside one.
Im pretty sure Honda didnt line bore them, but used a big milling cutter
....form tool.....and simply squeezed the head and cover together around
the spinning form cutter.

Being bigger on the inside journal, im hoping that it took less
damage/wear and I only have to bush the outside one. I can live with
some slop on the inside..the outside carres the points cam

Thanks

Gunner

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary
that Roosevelt would be remembered as a great president, "maybe even
alongside Washington and Lincoln," opining that Roosevelt "had every
quality that morons esteem in their heroes.""