Can we clarify the jetting question?

[FastCletus]

4 into 1 with stock airbox running 68 and 100.  Has a hard time starting, and boggs at 7K on hard acceleration.  

From what I have read the better scenario is 75 /105

Is that correct?

[TOOLS1]

Do some plug chops, and you will know for sure.
TOOLS

[Lucky 1]

First off with a stock air box all that is usually required is a mixture adjustment,
And you can increase the main for insurance against a lean WOT.

You cannot just change the main jet and solve all the problems.
Matter of fact the mainjets only control part of the throttle that is not even used that much.

Break it down this way:

Idle.... Controlled by the idle jet and mixture screw.

Midrange 1/4 throttle -3/4 throtttle is THE most critical
because that is what is used for most of your driving.

Main jet is for WOT and a little cross over into 3/4 throttle at the top of the range.


So to just change the main jets and think you have solved the problem is not going to work.
When you give it a quick twist of the throttle, the engine should immediately rev up
and not bog, or stall, or hesitate.

[FastCletus]

The bike like I said has a hard time starting on cold, and staying idling, and as well as coming out of first gear.  Once the bike is good and warm (about 20 minutes of riding) first gear is not too much as much of an issue, but I have still stalled it a few times.

Riding just generally around town I don't have that much of an issue. But when I need to "get on it" to get in to traffic on free way is when the bike boggs down.  Also when I go and ride the twisties and hit it coming out of a turn, "cough, Chug, vroom"

I really want to do a track day on this bike so with that being said I will be riding in the 7K range a good bit

My air mixture screws were turned out about 1.5, so last night I took them to 2 turns out, as I read someone else took theirs to 2.75 turns out.  Thought that was a big jump, so I thought 2 was a good start.  Will try it today as soon as sun comes up and see what 2 turns out is like.

[FastCletus]

Just fired it up. The two turns out made a big difference.  Fired up alot easier.  Throttle seems more respsonsive. Have to take a ride and see

[FastCletus]

Results
1st gear is much better, idle is a little high but I can adjust it down

High RPM's is horrible. Only unless you take your time to get to 60 will it do it nicely, other than that its just bogging down

My prognosis is to adjust the air fuel screw back .25 turn and see what happens.  My guess is that low end will be fine and top end will still struggle

Then I will jump to a 105 main, and see what happens

[Lucky 1]

When you have to turn the idle screw out that far it is a sure sign that the needle position needs to be altered. You even said two turns out on the mixture screw made a difference.

That hesitation you talk about is because of a too lean condition from 1/4 throttle.
I would increase the idle jet also.

Make one change at a time.

[seestheday]

This might help
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

[jerritt]

I have an 82 with 4 into 1 ker ker can and pod filters and I run 82 and 115 this got rid of any flat spots

[FastCletus]

ordered 73's and 105's.  According to  the book my bike should have a 68 and a 103.  Mine had a 68 and a 100.  I think 73's and 105's should do the trick

[barelycompetent]

I have an 81k with pods and 4-1 exhaust.  Im running a six sigma jet ket, 120's in 1 and 4, 122.5 in 2 and 3, and 75's on the mains.  My needles have been shimmed up with 2 washers per the kits instructions, and 2 turns out on the air flow screws.  I just put new carb boots on it the other day because I was still getting a high idle after it warmed up and that solved that problem.  My bike has good smooth acceleration thru all positions, and runs very well with the kit.  The total kit was 80 bucks for my bike, and the directions were very straight forward and easy to follow.  I would recommend them to anyone with the same mods as I have.  Check them out and see what you think.  http://www.6sigmajetkit.com/

[seestheday]

Why the different jets in 2 and 3?

[barelycompetent]

Sees, to be honest thats what the directions called for lol.  My theory on it though is because the 2 and 3 carbs are the inboard carbs, and with pod filters wouldnt pull the same amount of air as the outboard carbs with the same size jets.  Again, thats my theory, dont know why the instructions called for it, but I do know that it works well in my bike and my bike runs great with the kit and adjustments I have done to it.

[FastCletus]

If I had hair to pull out I would.  When I got my first cb750 it didnt have a breather box.  And the world told, the bike would never run good without it.  so I got one . Now I see all these people running PODS.  What gives.  I never looked to far into it as so many people said no.  I guess if you are proficient in changing Carb jets than a pod is not bad?

[barelycompetent]

Its really a matter of personal preference I guess.  If you dont mind working on and tinkering with the carbs ALOT, then pods arent bad at all.  Most people say that these bikes with cv carbs will never run right with pods.  They do take alot of work, but I cant really answer that because I have never run this bike with a stock air box.  I like how my bike runs with pods and the jet kit I put in, and I dont mind tinkering with them constantly lol.  So really if you dont mind doing the work then pods arent bad, if you are more of a set it and forget it kind of person then definitely dont try pods.

----- Original Message -----
From: FastCletus [via Honda CB750'S] <[hidden email]>
To: barelycompetent <[hidden email]>
Sent: Tue, 04 Jun 2013 11:53:19 -0400 (EDT)
Subject: Re: Can we clarify the jetting question?



If I had hair to pull out I would.  When I got my first cb750 it didnt have a breather box.  And the world told, the bike would never run good without it.  so I got one . Now I see all these people running PODS.  What gives.  I never looked to far into it as so many people said no.  I guess if you are proficient in changing Carb jets than a pod is not bad?

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[seestheday]

General consensus also seems to be that pods are a cosmetic upgrade only.  With a lot of tinkering you can get back to the real world power than you got from the stock air box...

Correctly tuned velocity stacks appear to be another matter.

[FastCletus]

Just to let anyone out there who feel silly when they make a mistake I did it too!!

FYI when you rebuild carbs make sure and put proper jets in the right place.  Primary in primary & secondary in secondary.  I just determined that mine was running half and half
Typical cletus, just typical

[FastCletus]

update
Got the 73's and 105's in and tuned.  had a small issue as my carbs werent on tight enough.  so fixed that and rode around town, stopping and tuning.  Got the bike 90% perfect, but I am 3 turns out on the 105's which makes me think that the 108's would of been a better choice.  
Revs and starts great, although a little rough until it gets warmed up, but usually fires up after 2 or 3 turns from starter.  when warm fires right up.  It still feels a little bogged down around 5K.  With three turns out.  Does anyone run theres with more than 3 turns out?