Author Topic: Keihin PD 42A rebuild/parts help... (Read 13115 times)

Thor's Hammer! · « **on:** December 28, 2009, 08:09:03 PM »

Today I got my 78F running with the correct model PD 42A carbs.

..first time running these carbs on the bike. the bike came with a mid 80's night hawk set as identified here:

http://forums.sohc4.net/index.php?topic=55978.0

I did the flash light bench sync and used new honda o-rigns in the PD 42A, but noticed that cylinder 1, 3 and 4 were running at normal or close to normal temperature at the exhaust headers. Cylinder #2 was barely warm. I know all 4 cylinder are getting good spark and really think the problem is carb related.

With this being my first attempt at rebuilding carbs, I made a mistake with the needle jet holders. Thinking these guys weren't seated far enough into the carb bodies I tightened them a little too much and mushroomed them a little where they push against the needle jets.

Dumb ass move on my part, i know it now

So, faced with needing to replace 4 needle jet holders, it seems to make sense to replace the other items included in a normal full rebuild kit.

I looked at the keyster kits (http://www.siriusconinc.com/pro-detail.php?pid=&product_id=455) but find the need jet holds aren't included.

Also, these kits are $40 each which seems kind of pricey, plus however much the needle jet holders will cost.

At $160+ for parts, and not knowing for certain I can get these things dialed in right, would it make better sense to get Cycle Exchange to refurb them or get a rebuilt set from somewhere?

1. Are there decent rebuild kits to be had for cheaper than this?
2. Where to get new needle jet holders?
3. While I really cleaned the slow jets and passages, did the bench sync and did my best rebuilding these carbs, is it possible the mushroomed needle jets account for the #2 cylinder running cold or would I be better to check float height?

Sorry to ramble, thanks as always for any direction.

dansvs · « **Reply #1 on:** December 29, 2009, 08:49:20 AM »

check this link
They have many different carb kits with lots of parts
http://cgi.ebay.com/ebaymotors/HONDA-CB750-CARB-CARBURETOR-REBUILD-KIT-4-KITS_W0QQitemZ110474953235QQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item19b8d20213

Thor's Hammer! · « **Reply #2 on:** December 29, 2009, 09:00:57 AM »

Thanks Dan!

I sent the seller a note asking about these kits for my Keihin PD 42A.

$89 for 4 kits I can live with when they come with needle jet holders.

Flying J · « **Reply #3 on:** December 29, 2009, 09:04:39 AM »

did you mess up all 4? I may have a few lying around i could send you for cheap. Rebuild kits are $$$$$ i have never bought any but wonder if i did, would it make the whole process a lot easier? I have rebuilt mt PD 42A s many times, making adjustments for exhaust and air filters. When you clean, check all passages and make sure your accl. pump is working. Issues i had with mine was at starting i would only get 3 of 4 cylinders to fire. 1 of the choke butterflys was not closing all the way. Where did you get this set of carbs? Is it stock jetting and are the needles at the stock height, oh wait they are not adjustable. I have been able to rebuild with fairly good success but when i do run into issues i always wonder if it could be a carb problem because im running old used stuff. If you buy new that just takes one less possibility out of the equation. But to me that 140 has not been worth it......yet. If the $84 kit is true let me know.

Thor's Hammer! · « **Reply #4 on:** December 29, 2009, 09:16:19 AM »

Thanks FFJMore.

See, that's my feeling as well. The rebuild kits are $40 each for the keysters and they don't have the needle jet holders. Honestly I am not sure at that the slight mushrooming matters here or not. 3 of the 4 cyclinder fire with the PD-42A. With the old VE54A, only two cylinders (3 & 4) would fire.

I got these carbs from a fellow member here and they were terribly filthy...I mean really, really bad.

Part of me wanting to get the carb kits is I wonder if the float valve springs are stiff/strong enough and I know one of my needles got bent during reassembly (I bent it back as best I could). The straightened needle was not in the #2 carb though and that's the one not given enough (or maybe too much) gas to the cylinder resulting in a cold exhaust for that cylinder.

I'll pull the carbs and take pics of the needle jet holders.

Flying J · « **Reply #5 on:** December 29, 2009, 09:30:29 AM »

Before you pull the carbs try and run it again. Use a fresh plug in #2. Does it fire up? Does it warm up when you give it more throttle? Pull the plug.
is it wet or is it dry and white? I dont think it would be a float problem. Well at least a mechanical issue. It the float valves are not working you will get fuel out the over flow tubes. Now an issue with the floats would be that you set #2 at the wrong height. Check the height difference with clear tubing.

dansvs · « **Reply #6 on:** December 29, 2009, 09:51:23 AM »

CLEAR TUBING!!! What an ingenious idea. I should have thought of that being a plumber.
Also, if you havent seen this manual, it helped me get back into the swing of things with carbs.

http://www.vf750fd.com/vf750f/Honda_Common_Service_Manual.pdf

Flying J · « **Reply #7 on:** December 29, 2009, 10:06:09 AM »

Another great source thats right under your nose is the SOHC4 website.
http://www.sohc4.net/index.php?q=content/fuel-system-carburetion

Thor's Hammer! · « **Reply #8 on:** December 29, 2009, 12:33:16 PM »

Thanks guys! I'll look over those link/references.

I got word back from the seller on ebay about those rebuild kits for the PD 42A...

~~~
No Mike, I don't have this kit, sorry. Rob

- usa-motorcycles-inc
~~~

No joy for those of us with a 78 CB750F.

I am gonna play some more over the next couple of days after reviewing the new suggestions.

Will update as I know more.

Ross Davis · « **Reply #9 on:** December 29, 2009, 06:30:13 PM »

I live in Orlando and have these carbs. I do not think you have ruined them. They have a slight concave curve to them. These have a pushed in idle jet, is it clear? Does it run on #2 after opening the throttle? It also houses the accelerator pump and main fuel supply. If the level is low here it must be the float assy. I have seen these with clogged accelerator nozzles act like this.

Thor's Hammer! · « **Reply #10 on:** December 30, 2009, 07:29:37 AM »

Quote from: Ross Davis on December 29, 2009, 06:30:13 PM

I live in Orlando and have these carbs. I do not think you have ruined them. They have a slight concave curve to them. These have a pushed in idle jet, is it clear? Does it run on #2 after opening the throttle? It also houses the accelerator pump and main fuel supply. If the level is low here it must be the float assy. I have seen these with clogged accelerator nozzles act like this.

Hey Ross!

Yes, these are the pressed/pushed in slow jets. I removed all four and made sure the super small main passage in each was clear along with the other holes in the top portion of each jet, so yes, they should be clear. I am using fresh gas with an in-line see through filter as well.

#2 exhuast remained mostly just warm after high idle and then onto reving up and down and back to idle over a 5-10 min period on 2 occasions now. All other cylinders were outputting hot at the exhaust although some were hotter (#4)...all would instantly vaporize the water misted onto each....except #2.

If you feel froggy Ross and are up for a ride out to Clermont, another set of eyes couldn't hurt the situation?

Mike

Flying J · « **Reply #11 on:** December 30, 2009, 08:05:48 AM »

Pull plug #2 and see whats going on in there.

Thor's Hammer! · « **Reply #12 on:** December 30, 2009, 08:27:45 AM »

Thanks ffjmore.

It is black...too rich, but honestly I can't say if it's from before or the result of the current way it's running. It wasn't wet when I looked at it though.

I think maybe I will grab a new set of plugs if I can find any locally and install a clean fresh one in #2 so i have something meaningful to go off of.

Flying J · « **Reply #13 on:** December 30, 2009, 08:36:53 AM »

I get my plugs from the local parts store, Pep boy or o'rileys works also if you can now or before you pull the carbs and have your airbox off make sure all your choke butterflys are fully open. Could be to much fuel but could also be to little air

Thor's Hammer! · « **Reply #14 on:** December 30, 2009, 11:24:40 AM »

Called NAPA. They have 'em

Hopefully a damn 18mm spark plug socket too!

NGK D8EA to be gapped at .6-.7mm

Thor's Hammer! · « **Reply #15 on:** December 31, 2009, 10:11:32 AM »

Quote from: ffjmoore on December 29, 2009, 09:30:29 AM

Before you pull the carbs try and run it again. Use a fresh plug in #2. Does it fire up? Does it warm up when you give it more throttle? Pull the plug.
is it wet or is it dry and white? I dont think it would be a float problem. Well at least a mechanical issue. It the float valves are not working you will get fuel out the over flow tubes. Now an issue with the floats would be that you set #2 at the wrong height. Check the height difference with clear tubing.

ffjmore...could you explain this procedure a bit? I haven't read anything about using clear tubing to check float height.

I did a google search and found this process, but it has you doing it off the bike:

http://www.xs11.com/xs11-info/tech-tips/maintenance/carburators/66-carburetor-float-balancing.html

Is this method (while carbs are installed on the bike) effected by tubing length or angle when doing the comparison or is it just a matter of gravity and the gas exerting fluid pressure when the tubing is placed at the float height?

Sorry for the questions, just never done this before.

Thanks, Mike

Flying J · « **Reply #16 on:** December 31, 2009, 10:58:38 AM »

To see the actual height in each bowl you nedd to hold the tube at the center of back of the bowl you are checking. If its held to the side like in the picture and the bike is on an angle you will get a false reading. I was trying to get a general idea of where my float heights are relative to the others. i was having an issue with one carb and was trying to find out if it was lower then the others.

Use clear tubing and crack open the drain thats it.

Thor's Hammer! · « **Reply #17 on:** December 31, 2009, 02:11:14 PM »

Installed one new NGK D8EA plug gapped per spec in #2 cylinder. Ran the bike for 15 mins or so, let it cool for about 30 mins, then ran it again for about 10mins. I had the choke on for some of the time as it needed to be on to keep the bike going. After maybe 5-7 mins I was able to take the coke off.

Here is the new plug after a total of about 25 mins revving and idling in the garage (can't ride it yet).

This is the old plug from #2 although the bike had different carbs for much of the time sense last time it was replaced (no idea how long ago that was). This plug did also run with in the bike with the rebuilt PD-42A's...but only for maybe 20 mins or so.

Here it is just for reference:

And lastly...here is some video of the bike running although I am not sure how much (if any) help it will be as the audio doesn't sound great.

[youtube=425,350]<object width="425" height="344"><param name="movie" value="

name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="

type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>[/youtube]

Flying J · « **Reply #18 on:** December 31, 2009, 09:06:43 PM »

You are running a bit rich, you think. So what could it be? You could always move the needle to a different carb and see if the problem follows the needle. It could be a weak spark. To check that switch the plug wires on 2 and 3 and see if the problem moves to # 3. Thhats all i got for now.

Thor's Hammer! · « **Reply #19 on:** December 31, 2009, 09:40:42 PM »

Thanks man.

Yeah...rich it is. Tomorrow the carb come back off. I will set the float heights and try the homemade manometer...never used it on a bank of carbs though...only on my old V-Star twin with 2 carbs.

Also gonna look at the accelerator pump adjustement per the manual.

Valves may get adjusted too...maybe they are off for #2.

Will keep y'all updated.

Flying J · « **Reply #20 on:** January 01, 2010, 10:50:43 AM »

Thats a good starting point. And if that doesnt fix it, you will at least know its not any of those things. Keep us posted.

Thor's Hammer! · « **Reply #21 on:** January 01, 2010, 01:53:13 PM »

FIXXXXEDDDDDDD!!!!

I adjusted the valves this morning...only a little tight, honestly better than I expected. Doubt this had an effect.

Installed new plugs in the other 3 cylinders. Doubt this made a difference either.

Pulled the carbs again and set the float height to 15mm. #2 carbs was ~ 1.0 to 1.5 lower than the rest. Also pulled the slow jets from #1 and #2 and cleaned again as they were clogged. Also did a visual bench sync...no flashlight method.

#2 cylinder now runs nice and toasty like the other at the exhaust side. #4 is a little cooler now too where it was the hottest of the 4.

I haven't done a regular sync yet (only have homemade manometer) but I think it will finish off any irregularities (not obvious to my untrained eyes) between the cylinders.

Thanks guys for the suggestions and guidance!

Flying J · « **Reply #22 on:** January 01, 2010, 02:08:02 PM »

Way to go. Its nice when things all come together. It always makes me really happy when my bike is running great.

Ross Davis · « **Reply #23 on:** January 17, 2010, 07:32:49 AM »

Sorry I have been in Europe. Glad it is repaired. Did you get a chance to sync the carbs?

lucky · « **Reply #24 on:** March 23, 2014, 04:30:49 PM »

Quote from: Flying J on December 29, 2009, 09:30:29 AM

Before you pull the carbs try and run it again. Use a fresh plug in #2. Does it fire up? Does it warm up when you give it more throttle? Pull the plug.
is it wet or is it dry and white? I dont think it would be a float problem. Well at least a mechanical issue. It the float valves are not working you will get fuel out the over flow tubes. Now an issue with the floats would be that you set #2 at the wrong height. Check the height difference with clear tubing.

This method is not right and will not run right.
The fuel level will be above the overflow drain tube inside the float bowl.

Measure the float level like the book shows you.
Forget that"clear tube method".

News:

Author Topic: Keihin PD 42A rebuild/parts help... (Read 13115 times)