Topic: Did I ruin my jets?

[kerryb]

I cleaned my first set of carbs, '77 750K.  After the second cleaning, and four or five installs with limited success, I ran a drill through the slow jets. (I know, not too bright, but it was late and I was desperate).  Success! now it runs and idles and starts great.  Trouble is, when I rev it up, there is some the black smoke...Too rich maybe?  So the questions are...
What size is a number 40 slow jet?
Can I get new jets to replace these, and where?  My local shop says they are not to be had new.
The drill bit is .024 inches, how far off am I?  The other not-cleaned-yet jets look waaay smaller.
thanks. kerry

[scottly]

A 40 is .4 mm, =.0157" A small increase in diameter has a much bigger surface area, which relates directly to flow.

[kerryb]

Thankyou Scottly,
I'll run these while I try to source replacements.  Any suggestions, besides buying more used carbs.
I have a lathe, I wonder how hard it is to plug and drill these to the right size?

[bryanj]

Try reading this page

http://www.motorcyclecarbs.com/Keihin_Pilot_Jet_N424-22_Press_C2453.cfm

NOTE i have not used nor dealt with this supplier so cannot vouch for anything stated

[eurban]

You can download the factory manual for the 78ks and Fs here:
  
http://www.mediafire.com/?5ttzdg9yyuz

It should be applicable to your 77k for almost everything.  Stock  pilots are #35's not #40 and you have created aproximately a #60 jet with your drill bit. Needless to say, this isn't going to work properly.  Plugging and drilling isn't a good option as the jets are simply more than just a shaft with a hole. The metering point of the jet is in the middle and it opens up to a larger diameter near each end. Also there are side holes.  I wouldn't use the screw in type jets from with the motorcyclecarbs link since you can actually buy press in style jets from:
 
http://www.siriusconinc.com/pro-detail.php?pid=&product_id=1107

Stay away from those drill bits!

[Don R]

A Po did that to my F but he apparently drilled everything, at least you know it happened. I have a 75F but was able to buy them all new.

[david 750f]

The problem with drilling jets is that a drill almost always drills oversize. There are specialty reamers in small sizes but they are expensive. The jets are relatively inexpensive and still available from Honda. (and will last another 30 years)

[Gordon]

The problem with drilling jets is that a drill almost always drills oversize. There are specialty reamers in small sizes but they are expensive. The jets are relatively inexpensive and still available from Honda. (and will last another 30 years)

Also, the idle jet isn't one diameter all the way through.  It's larger on the bottom half and then steps down to a smaller diameter inside the emulsion tube.  And if I'm not mistaken, the hole in the main jet is tapered. 

[Don R]

If you went into the main jet and went too far the needle jet is above it also, that's what was wrong with my bike. I didn't know there was another jet in there until the guys here educated me.

[kerryb]

Thanks everyone,
yes I did ruin them, but learned a bunch in the process.  I took jets from another carb, put those in and it runs good without smoke.  Now I have to research the new problem of stumble on acceleration (bike not on road yet)  You don't suppose it could have anything to do with two clogged accellerator nozzles do you...I promise, NO DRILL BITS!
have manual, will read more.
Ordered new jets from Sirius.  I'm still new to this so everything takes sooo long to do.  No, I haven't reset the timing, valves, or seat height yet.  Those are coming.

Thankyou all, it's nice to be here
kerry

[Motoguy23]

And if you feel like cleaning your jets out I've heard that the tool that people use to clean oxy acetylene torch orifices works.

[BobbyR]

Thanks everyone,
yes I did ruin them, but learned a bunch in the process.  I took jets from another carb, put those in and it runs good without smoke.  Now I have to research the new problem of stumble on acceleration (bike not on road yet)  You don't suppose it could have anything to do with two clogged accellerator nozzles do you...I promise, NO DRILL BITS!
have manual, will read more.
Ordered new jets from Sirius.  I'm still new to this so everything takes sooo long to do.  No, I haven't reset the timing, valves, or seat height yet.  Those are coming.

Thankyou all, it's nice to be here
kerry

I have a 78K and your accel pump is probably gummed up as are the nozzles. The pump only holds a tiny amount of gas so it spoils quickly. To avoid damaging anything (as I have done) simplyy use a strand of copper wire from a lamp cord or the high E guitar string. The copper is better since it is softer metal. It loosens the junk and you spray it out with carb cleaner. The accel pump you simply remove the screws and clan out the gunk. Once you do this carefully, you will notice better throttle response.     

[traveler]

I agree.  Get some #12 AWG stranded electrical wire, and cut out 1 strand.  Copper is of course softer than brass, so it won't so anything to the jet other than clean any crap out of there.

~Joe

[eurban]

Yes to the above suggestions. . . .For proper performance, these carbs require the accel pump to be working properly.  You will definitely notice acceleration stumbles without the accelerator pump doing its thing.  Do a comprehensive tuneup on the bike. All systems must be up to snuff!   

[Franken750]

Question: Would you poke a piece of scratchy wire down inside your schlong?

No?

Fancy that. 

Treat the orifices in your carby's with even more respect.

 

[Motoguy23]

Question: Would you poke a piece of scratchy wire down inside your schlong?

No?

Fancy that. 

Treat the orifices in your carby's with even more respect.

 

Thanks for this comment.  I think I'll cringe every time I clean my carbs from now on.

[kerryb]

Update.....GOOD NEWS!.......Everything you guys said would happen in the other carb threads, did happen.  So I went back in and cleaned it all again, more carb soak, more compressed air, one teensy little strand of copper wire in an exacto knife handle for reach and the accelerator nozzles are all clean, the jets are all clean and flowing, the rubber boots are sealed (I think). The accelerator pump diaphragm is pumping great.  and NO drill bits were harmed!

I still haven't set timing (can't find my timing light, misplaced in a flurry of moving stuff), or checked valve adjustment, or set seat height but....IT RUNS....It does the ZOOM thing.  It idles so well the idles stop screw is backed out completely and it just purrs.    Thanks everyone.  With choke, starts on one kick.

Just one more issue.  I sprayed wd40 everywhere looking for air leaks, can't find any, but the rpm's are a little slow to come down unless I pull the throttle return hard enough the compress the spring on the choke actuator linkage.  Then the rpm's drop instantly back to slow idle.  (mechanical tach says about 900 rpm)

Any suggestions of where to look next (or again as is usually the case here)?

[Lenny55]

I'm having trouble finding bigger main jets for my carbs, one of the mechanics at the shop I deal with says he has special bits for jets and it would be easy to drill them up from the stock #100.

I thought it sounded good untill I read this thread.  Is it really possible to professionally drill out jets?

Thanks, Lenny.

[eurban]

Update.....GOOD NEWS!.......Everything you guys said would happen in the other carb threads, did happen.  So I went back in and cleaned it all again, more carb soak, more compressed air, one teensy little strand of copper wire in an exacto knife handle for reach and the accelerator nozzles are all clean, the jets are all clean and flowing, the rubber boots are sealed (I think). The accelerator pump diaphragm is pumping great.  and NO drill bits were harmed!

I still haven't set timing (can't find my timing light, misplaced in a flurry of moving stuff), or checked valve adjustment, or set seat height but....IT RUNS....It does the ZOOM thing.  It idles so well the idles stop screw is backed out completely and it just purrs.    Thanks everyone.  With choke, starts on one kick.

Just one more issue.  I sprayed wd40 everywhere looking for air leaks, can't find any, but the rpm's are a little slow to come down unless I pull the throttle return hard enough the compress the spring on the choke actuator linkage.  Then the rpm's drop instantly back to slow idle.  (mechanical tach says about 900 rpm)

Any suggestions of where to look next (or again as is usually the case here)?

Did you bench synchronize the carbs before reinstallation?  Do a gauge synchronization and it may help your RPM drop issue.