Author Topic: main jet size question  (Read 1146 times)

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Offline andy8190

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main jet size question
« on: March 17, 2009, 01:01:12 PM »
so i am taking the carbs apart to put new orings in places and i notice 3 of my main jets is 95 while one is 100. I have 74 cb550k with uni airfilter and 4-4 exhaust. which should i be running the 100s or 95, and i am going to need to get new 100s if that is the case and just one new 95. Where can i get these cheaply. If at all possible i dont want to order new jets so can i just adjust the idle screw on that one different jet?
What are the results of running 95 vs 100?

Offline fdbrat

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Re: main jet size question
« Reply #1 on: March 17, 2009, 01:13:18 PM »
You should be running 100 if you want to be stock.
1975 CB750F
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5 ohm coils / 5k ohm caps
In- .05 / Ex- .08

San Luis Obispo

Offline andy8190

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Re: main jet size question
« Reply #2 on: March 17, 2009, 01:24:05 PM »
i saw that in faqs but what will running 95 do?

Offline motorhead55

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Re: main jet size question
« Reply #3 on: March 17, 2009, 02:33:52 PM »
Smaller jet size number means less fuel and leaner running.
1976 Honda 550F bought new in 1978
2006 Yamaha TW200 TrailWay
1967 Triumph 200cc Tiger Cub
2007 Dodge 5.9 Cummins Diesel, 6spd. Stick, 4X4
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Offline TwoTired

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Re: main jet size question
« Reply #4 on: March 17, 2009, 03:28:33 PM »
Stock is 100.

I wonder if those #95 jets were drilled out larger?  I was thinking maybe someone adjusted the carbs for higher altitude operation.  Odd they only three of four. ???
Do your spark plugs color unevenly?

What altitude are you at?

I think Spikeybike knows where to get new jets.  Might PM him or search his posts.


Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline andy8190

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Re: main jet size question
« Reply #5 on: March 17, 2009, 04:46:31 PM »
well the bike came from high altitude, pueblo colorado, but i live in fayetteville arkansas now, not very high prolly in the 3k, 4k altitude. i havent checked the spark plugs yet, i just wanted to get it running again first and then have a full tune up done. The guy who was gonna help me hasnt responded to a pm i sent him so i am getting worried i have no help anymore :(. There is this one guy at lowes who owns a 750 cafe i believe so i might go ask him if he minds teaching a newbie. The only real thing im not sure of is the valve adjustment and cam chain adjustment. Also i noticed today my shifter is definitely leaking oil so prolly needs a new oring in there and i heard that is a pita to do. On a good note i road it around for a while today and it road fine, except for trying to get it into neutral at a stop after the engine is hard.

Offline TwoTired

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Re: main jet size question
« Reply #6 on: March 17, 2009, 05:44:52 PM »
Also i noticed today my shifter is definitely leaking oil so prolly needs a new oring in there and i heard that is a pita to do. On a good note i road it around for a while today and it road fine, except for trying to get it into neutral at a stop after the engine is hard.
The shifter shaft seal is not a simple oring.  It's easy to replace if you know how.  There are past thread on this.  I pierce it with a small sharp screw driver near the outer circumference, and it pries out easily.

The neutral problem you describe is caused by the clutch dragging.  If adjustment doesn't cure the issue, and oil change may help, or a change in brand, or viscosity.  I don't know what you have, now.
If that doesn't cure it, then probably you have warped plates in the clutch.

If you can't learn to anticipate getting to neutral before you're stopped, or if it won't snick into neutral by slight fore and aft movement of the bike, clutch work is about the only other way to fix the issue.

I'd start with adjustment, though.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline andy8190

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Re: main jet size question
« Reply #7 on: March 17, 2009, 05:49:22 PM »
yeah i have been reading about the shifter seal.
And also i know to shift into neutral before stopping but i didnt when i pulled into the garage today and had to back out and then come back in haha.
I am not sure which way to adjust the clutch to fix this but will try what i can, any suggestions?

Offline TwoTired

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Re: main jet size question
« Reply #8 on: March 17, 2009, 05:53:35 PM »
I am not sure which way to adjust the clutch to fix this but will try what i can, any suggestions?

Er, you mean you don't have the Honda shop manual yet?  That's what I learned from.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline andy8190

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Re: main jet size question
« Reply #9 on: March 17, 2009, 05:55:27 PM »
yeah i do have it and adjusted it to the play length it says to adjust to and that doesnt do much to the neutral problem. It shifts through gears just fine but that neutral is just hard when its hot and I am at a dead stop

Offline andy8190

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Re: main jet size question
« Reply #10 on: March 17, 2009, 05:56:32 PM »
and castrol 10w-40 is what is recommended right?

Offline TwoTired

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Re: main jet size question
« Reply #11 on: March 17, 2009, 07:34:34 PM »
yeah i do have it and adjusted it to the play length it says to adjust to and that doesnt do much to the neutral problem. It shifts through gears just fine but that neutral is just hard when its hot and I am at a dead stop

Sounds like you are describing the cable adjuster.  You adjust that AFTER you make the adjustment near the bottom of the clutch cover.

As for oil, I hesitate to get into this.  But, it might be worth your while to try some 10W-40 Honda HP-4 without moly at your next oil change.  If it helps your problem (possibly), it is cheaper and more convenient than doing a clutch job.
It's your call, of course.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

cherry bomb

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Re: main jet size question
« Reply #12 on: March 18, 2009, 07:42:50 PM »
time to hijack another thread...mine didnt get a response maybe this one will...my 77 cb750f has got stock 105's for the mains...im running low boy straights and K&N pods...should i go to a 110 or 115 to get the thing running right? Also...re-jet then sync or sync then re-jet?