Topic: 78 f2 rebuilt running very rough

[jus750]

Hey members after 6 months of building I have finished my f2, well close i filled the fuel tank, which leaked and ruined my paint work, braised it and further stuffed the paint. Any way i have a hooked up a temporary fuel supply so i can try and tune her. Problem is the engine runs very rough, It starts nicely, does not idle below about 1300rpm and wont rev smoothly, The longer it runs the worse it gets, I dont want to rev it to much but it wont rev past about 4000rpm anyway without coughing and sputtering
I have
rebuilt motor new rings chain, headjob, It has pretty good oil pressure
stripped down and rebuilt carbs minus slow jet, which i dont know how to pull out any help would be great
set valve clearence,points plugs
set timing roughly (waiting for it to run a bit smoother so i can adjust with a gun
new air filter etc
clean fuel
any help would be great, I have done everything myself and are reluctent to take to a mechanic has anyone got any ideas
Standard pistons ans standard everything

[TwoTired]

The slow jets just yank out.  Be mean.  Must see light through them.

Also check the accelerator pump for function.

Check the head pipes for even heat. cool one point to a corresponding cylinder/carb issue.

Clean the points surface of invisible insulation.

Use new spark plugs, one that have super clean center insulators near the electrode tip.

Don't forget to vacuum sync the carbs.

Verify proper choke operation.

[jus750]

cool, do i grab them with pliers( slow jet), they are brass, I didnt want to damage them to much is pliers ok.
when i operate the pump by hand it makes a noise like it is sucking ? I did clean this area out It does not have much travel is this ok.
The head pipes seam to be an even heat, i will verify
True they are new points, I will give them a light sand to rid of the surface gunk
I have new ngk spark plugs I will als give them a light sand
I don't have the gauges yet to vacuum sync the carbs I am getting them soon
Thanks heaps for your help
How do you get the slow jets out ?
The chock works the butterflys evenly is this all i need to do to verify this

[TwoTired]

cool, do i grab them with pliers( slow jet), they are brass, I didnt want to damage them to much is pliers ok.

I use parallel pliers with soft jaws.  Some use a leather pad to minimize tool marks.  Tap them back in after cleaning.

when i operate the pump by hand it makes a noise like it is sucking ? I did clean this area out It does not have much travel is this ok.

With fuel in #2 bowl, you should see each of the posts in the carb mouth shoot a strong stream of gas into the carb bore.

True they are new points, I will give them a light sand to rid of the surface gunk

No sand. Silica is an insulator and little bits embed in the soft contact faces.  Sanding shortens point life and causes them to burn up faster.
File, ...or burnish with no wax cardboard.

How do you get the slow jets out ?

Yank them straight out.  I don't like the twisting motion others recommend.  Too much like a twist drill action that makes the refit less secure.

The chock works the butterflys evenly is this all i need to do to verify this

Motion is good.  I like to see full closure each station, and full open capability.

[jus750]

no worris i have a file for the points instead of the sand paper
Do you think it will be the slow jet, The carbs were pretty hard to install cause my rubbers are pretty hard, I will rip em of though if need be
I am pretty confident the choke is ok there is full movement and they close fully
I supose i will have to rip the carbs of to check the pump?

[TwoTired]

When you cleaned the carbs, how dirty were the insides?
Clogged pilot jets lead to cool head pipes for those cylinders that have the carb jet problem.
They also cause poor or no idle, since they are supposed to provide most of the fuel when the throttle is set to idle position.

If the carb couplers are too hard, they may not seal correctly.  And, leaking intake runners foil any hope of the carb's proper delivery of A/F mixture.
New carb couplers are quite a good thing.

You only have to remove the air box to see the accel pump squirters work Assuming #2 carb bowl is filling properly with fuel.

There have been past threads where the floats were installed upside down in the PD style carbs.  Just saying...

Did you bench sync the carbs?

[jus750]

The carbs were pretty clean
I didn bench sync them as i Dont know how my book does mention this. Is it hard to do,I think I am going to rip them of anyway to check.
I am pretty sure the floats are in the right way I will check this
Are carb boots still available, how much roughly are they.
I wanted to do the wintergreen oil trick but that stuff is a bit hard to come by over here in any decent quality

[TwoTired]

Bench sync is fairly easy, just tedious.  Vacuum sync is way better, and should be done regardless of a bench sync.  Bench sync will just get them close.
I like the light method.
#2 is your reference carb.  Ideally, you would back off the idle knob until the light was blocked in #2 carb.  If other slides prevent that, then open the others until you can *just* block the light on #2.  Then, without moving the idle knob, use the individual adjusters under the top cap to adjust, each of the other carbs so the light *just* gets blocked.   If you did it right, when you are done you can move the idle knob and all the carbs will block the light at the same time when the idle knob is backed off.

You could call Western Hills Honda to see if new carb couplers are still available.  Looks like $22 each.  It's worth it, IMO.
http://honda.westernhillshondayamaha.com/fiche_section_detail.asp?section=125222&category=MOTORCYCLES&make=HONDA&year=1977&fveh=2985

16211-410-000
16212-410-000
16213-410-000
16214-410-000

[jus750]

sounds good, I had a back up set of carbys that i was going to use on my second f2 i have already got the slow jets out of them and cleaned them, i will bench synch them and swap thee carbs tonight, will take a while but hopefully it will make a diff, thanks so much for your help

[Ace]

You mentioned in your first post on this topic that you set the timing roughly?  I found setting the timing on my F2 was more accurate with the bike not running.  I had automotive timing gun issues.

Did you have to replace any parts in the carbys such as the accelerator pump plunger, needles etc?

How many turns out did you set the idle mixture screws?

Are you running stock airbox/filter, did you have a look to see what size main jet you had (usually stamped on bottom of main jet or on the side)?  A bit more information and hopefully we can sort you out if you have any problems when you get the chance to take it down the street.

Bench syncing the carbs does work as TT mentioned.  I had a second set of F2 carbs, cleaned them, bench synced them and they ran quite well when put on the bike and also got new intake boots which helped make it idle (boots didn't seal so running lean).

[BlackMax]

Went through a similar situation after redoing my F2.  Rough and 1 or 2 cylinders would cut out.

Here's the thing:  when pull the plugs, are they back as night? If so, it's going to end up being the slow jets and/or the idle mixture (I'd go 2  turns out).  I also seemed to benefit a bunch from going with hotter plugs (can't remember which ones those are at the moment).

If that doesn't work, and you say the points are good, I'd look at the coils.   But most likely, idle mix and slow jet should do the trick.

[jus750]

Ok here is were im at
reset and filed the new points, the gap was way out I dont know how I managed to do this
checked the plugs 2 were pretty black
pulled down the carbs Bench synced them, not sure of main jet size.( forgot to look, spewin)
I am pretty sure the slow jets had never been removed, so I think the jets would be standard
Cleaned the slow jets( used pliers with a bit of leather on the jaw
when I tested the pump the spray was very weak so I installed a stronger spring now it sprays a good meter. even sprayaccross all 4
put it all back together and its running real nice, very responsive
revs nice, did not want to rev it to much but Im sure that side is ok
idles a little erratic, I need to get vacuum gauges
timming does not seem right also i will try without it running( with the gun it shows advance even at full adjustment)
Air filter is standard paper
plugs standard
standard bore (rings were pretty exe as Im sure you guys know, it has F2 pistons)
any ideas with Idling
when you rev it it takes a few seconds to go back to idle as well
should I try going out 2 turns
1 stupid question but is a turn a 360 deg revolution. I presume it is, or is it 180 deg. This would make a massive diff

[Terry in Australia]

G'Day mate, if it's taking a little while for the revs to drop when you back it off, it's sucking air. What are your intake boots like? Are they cracked? 1 turn of the air screw is a full 360 degrees. Cheers, Terry.

[jus750]

cool, the boots were pretty hard , they were not cracked in anyway, I was going to try the wintergreen stuff but found it pretty expensive in any sort of decent amount.
I just soaked them for a while in mothers back in black
they are  seated fully on the carbs and to the motor and i did the clamps up extra tight
It is possible they are leaking, what is an effective way to test for this ?
used the static method for timing and am pretty sure its spot on, will start the sucker in the morning and see how it goes.
are boots still available and how much roughly, Im in Sydney

[jus750]

Just read up spray a bit of wd40 on them and see if the idle changes, is this right?

[TwoTired]

Provided the carb boots are sealing...
For a smooth idle, you need the spark timing correct for all cylinders (not just some of them)
And you need a proper vacuum sync so each cylinder can pull the same vacuum and make equal power as the others.

In fact, tappet adjust (each cylinder being equal) can make an idle difference, too.  Do this before vacuum sync.

[jus750]

No Worries, I just Happen to have a day of today so Im of to the shed to do just this, Think I will have to invest in a set of wire feeler guages to confirm my tappets, would be good to get this sorted b4 my girlfriend gets back from her holidays