Tuning Carbs - 1975 3C w/ stock ignition

  • Thread starter Thread starter laverlesmains
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laverlesmains

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So my winter project is more or less complete..  at least the big bits, now it's down to tuning and riding.

I've seen reference to a dell'orto tuning manual - can someone send that to me?    She starts up and idles nicely - and revs nicely while in the garage.  Out on the street it runs up to about 3000 smoothly, but then bogs or occasionally backfires.   Want to make sure I've covered the basics in setup.

Thanks, Tim
 
Sounds like the transition from pilot jets. maybe look at the emulsion tubes or needle type?
Float heights ok?
 
G'day Tim

I have scanned copies of the Dellorto manual and parts books but the files are too big to post here as attachments.

PM me with your email address ans I'll send them to you.

Cheers,
Cam
 
dont mince your words Tim
yoiu should say what you realy mean, so what ignition have you got on yours then Timbo?
CLEM
 
PM sent - thanks for the manuals.

It's the original ignition system.  I've got a DMC awaiting install, but wanted to at least get the carbs setup after my rebuild..  besides, the DMC scares me so I have to ponder it for awhile.

Cheers, Tim
 
It sounds like it could be a float level problem,or insufficent flow from the tank.Unless the insulation on the pickup and coil wiring is falling off[vibration induced shorting].Or other electrical connection,ign. sw. kill sw. harness etc.
I'd start with the float levels and fuel delivery first.
 
I would tend to agree w/ fuel delivery..  will check floats & petcocks & ensure I've got enough gas in the tank!
 
well it appears to have been a fuel delivery issue - a little rerouting of the fuel lines & ensuring more than a cupful of gas in the tank seems to have done the trick.

despite the 105/40 degree weather yesterday she ran fine up to redline in the first three gears.  A little breakup of the ignition at higher revs, but the DMC should take care of that.    Fiddled about to rebalance the carbs, first w/ a mercury stick, and second w/ a TwinMax and all seemed to be fine.

Will give it a bit of a longer ride today.

Here are some random photos

Indicators installed, new gaiters...
IMG_0404.JPG


Brake rebuild time..  I had the sheared bleed valve spark eroded, but I'd buggered the threads a little too much for proper service..  It does hold a seal, and I did manage to bleed the system so the brakes work fine
IMG_0406.JPG


Rear angle - indicators, shocks and silencers installed..
IMG_0409.JPG


Carb balance time.. 
IMG_0410.JPG


And this is me (on the right) and my cousin Will (left) at his place in Philadelphia - for his son's wedding.    This is his restored 1963 Honda 305 alcohol dragster..  Nice original 4" Avon slick on the rear.  Everyone should have an alcohol fueled dragster in the garage !
S0121079.JPG



 
laverlesmains said:
I had the sheared bleed valve spark eroded, but I'd buggered the threads a little too much for proper service..   It does hold a seal, and I did manage to bleed the system so the brakes work fine
Click to expand...

Tim, I can tell you (from experience ::)) that the calipers can be Helicoiled/TimeSerted just fine when you buggar the bleeder thread. I'd suggest TimeSerts that don't have any opening between the inside and outside of the insert and because they do lock better than Helicoils.
But if what you have is working, WTF? Just remember to grease well with Teflon grease to seal the thread, or use Teflon plumber's tape.

Ken
 
Very nice, but she be a 3C not a 3CL. I also snapped off a bleed nipple, and then snapped off the tip of the easy out and the caliper is now at the engineers being spark eroded. If that fails I will use the back side off a non-threaded caliper I picked up and swap out the 1/2 with the buggered nipple - fortuitisely the rear side of the front right caliper.
 
thx for the correction on 3C.

re: teflon tape - I've got some, so I'll give that a whirl. 

cheers, tim
 
Not sure about the compatibility of ordinary plumbers teflon tape with brake fluid. The bleed nipples seal against the seat anyway, so the threads shouldn't need sealing tape.
However, it's sometimes an advantage to use thread tape to stop leaks while bleeding the system. I have a pressure bleeding setup which tends to push a bit of fluid out past the threads. I've used the oil/gas resistent thread tape and it seems to deal with brake fluid OK - at least for as long as it takes to bleed the system.

Cheers,
Cam
 
Brand new calipers are available at reasonable cost- probably way less than a rebuild if spark erosion needed.
 
Ah.  Well in that case replace with four pots and enjoy luvverly braking at the expense of a little originality. :D
 
Reggie3cl said:
Ah.  Well in that case replace with four pots and enjoy luvverly braking at the expense of a little originality. :D
Click to expand...

Got a pair sitting here as well as a later mastercylinder to suit - but have to get the bike past the pernickity ones at the registration inspection before I can start changing things around.
 
Reckon the original master cylinder would do just fine- much better match to the 4 pots than the o/e calipers..
 
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