Help needed. Do I have a carb problem ?

Post Reply
daves79x
ICOA Technical Director
ICOA Technical Director
Posts: 4738
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA
Location: Knox, PA

Re: Help needed. Do I have a carb problem ?

Post by daves79x »

Your symptoms are indeed a bit strange. I would, upon disassembly, check for sticking slides, proper placement of the primary and secondary mains, rubber idle jet plugs intact and in place.

In addition, I don't think you mentioned pulling the advancer. You should do that and check for proper assembly and operation.

Dave

JustMike
Forum Regular
Forum Regular
Posts: 65
Joined: Fri Jul 20, 2018 7:14 pm
Location: Scotland
Location: Scotland

Re: Help needed. Do I have a carb problem ?

Post by JustMike »

Hi Dave, thanks for your comments.
Strange it is indeed.
The very first thing I checked was the ignition timing and I also removed the advance retard to check it was working freely.
On removing the carbs the first thing I`ll check is the injector pump and chokes and throttle butterflies. I need to know if there is any issues with them before diving in.
The next thing will be the slides, diaphrams and needles.
Then it will be float levels, and then the jets before moving onto poking around in all the holes.
Hopefully that way I`ll be able to eliminate each component as I go along.
I don`t want to just dive in and strip everything out without ever knowing if a particular item was causing the problem and I`ve missed it because I just dived in.
Fixing the carbs is the goal. But fixing them and finding the problem at the same time will be the cream on the cake.
I am aware of this particular problem with the jets being in the wrong place Dave so will be taking note, and I have seen comments about those rubber plugs being loose.
That makes me wonder if when the clown from the garage I bought the bike from was in the carbs fixing the fuel leak prior to ne getting the bike, has lost one. Hmmmm


Mike

JustMike
Forum Regular
Forum Regular
Posts: 65
Joined: Fri Jul 20, 2018 7:14 pm
Location: Scotland
Location: Scotland

Re: Help needed. Do I have a carb problem ?

Post by JustMike »

Dave I have the carbs out now.
The jets are in the correct holes and the rubber bungs are there for the idle jets.
First thing I checked was the injector pump and it was not working on 2 cylinders, 3 and 5 I think it was.
The idiot garage mechanic who`d been in there to fix the fuel leak before I got the bike has changed the float bowl seal for some cheap shite article.
I know the carbs were rebuilt using Randakks kits as I have the receipts for them. Now I have one float bowl with a seal that has expanded in size after opening the bowl and I`ve no chance of getting it back in.
One kit to order at least.
I`ve taken out the primary and secondary jets and the emulsion tubes and they are all clean, but I`ll leave them soaking in carb cleaner anyway.
The idle jets have been tapped for removal already. But no idea to what size thread. So I`m on the hunt for small screws to try. But the bike ran like a dream at low revs and at idle so probably they`ll be okay.
The chokes all operate as expected with no stickiness as do the throttle butterflies.
The slides all seem to be fine with no noticeable gum on them. But I`ve cleaned them anyway.
I still have to check float levels but I might leave that till last.
After tea I think I`ll spend an hour spraying cleaner into the passageways and leave it to soak overnight.
Mixture screws were all set at 2 1/2 turns. I think I`ll set them all at 2 and then start from there when I put the bike back together.


Mike

daves79x
ICOA Technical Director
ICOA Technical Director
Posts: 4738
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA
Location: Knox, PA

Re: Help needed. Do I have a carb problem ?

Post by daves79x »

Even the Randakk bowl gaskets/seals will expand when exposed to fuel. I do not think Viton bowl gaskets exist. Just let the expanded gasket sit on a newspaper overnight and it will return to the correct size. Also use this opportunity to check the throttle plate sync, but sounds like your idle is OK. Be very particular about the float level - I've seen them set very, very wrong. Verify flow through the 3 small holes in the carb throat through the pressed-in jet. You have to thread a screw into the adjacent jet tower and thread a pilot jet in it's receptacle until it's completely seated to check this correctly. Otherwise, brake cleaner (that's what you do the checks with) will spray everywhere.

This one is going to be tough. There is something obvious somewhere and it may not be in the carbs. Have you checked the fuel flow from the petcock? Do you have an overly-restrictive filter in-line?

I'm not sure I'm crazy about your coil/wire set-up. Seems like that's been a hit-and-miss (no pun) affair. I would be absolutely certain all coil wires (primary and secondary) are matched up correctly, ground wire good, voltage to the primary side correct.

Your bike needs really gone over with a fine-toothed comb to verify every component is correct and functional. It might not be easy.

Dave

JustMike
Forum Regular
Forum Regular
Posts: 65
Joined: Fri Jul 20, 2018 7:14 pm
Location: Scotland
Location: Scotland

Re: Help needed. Do I have a carb problem ?

Post by JustMike »

Hi Dave thanks for adding more food for thought.
As it happens, this morning I managed to get in touch with the person who rebuilt the carbs and can confirm that he does in fact know his job.
What a guy. He was on the phone with me for ages going through things and actually remembers doing the job. Then a few hours later he calls me back to say he had spoken to the previous owner that he`d done the job for and added some more pieces to the jigsaw. What a service and all out of the goodness of his heart.
Unfortunately he too is stumped, but ran through a list of things to try while I have the carbs out on the table.
What you say about the bowl seal has in fact happened, but as yet it hasn`t come back fully, but I will replace it to make sure it will be okay. The other 5 are fine.
I have done all that I am doing today and my next job will be checking all the float levels and then double checking. I want to spend some time on them and make sure.
Today I removed the idle jets and using a "special" magnifying glass, that can show the machining marks on the jets, to inspect every hole and also up inside the jets. They look clean but I suspect there might be some small flakes floating about in there somewhere, so I`ve left them soaking overnight in carb cleaner.
I did in fact blast cleaner up inside the jet posts and into every passage I could see. Yes it was going everywhere lol. Including out those holes in the carb throats.
Also after giving the carbs a really good flush out I switched on the compressor and gave them a really good blow out with air. Got covered in cleaner again lol.
Oh I forgot. Most of the orifice cleaning was done with the air mixture screws still in place. For the last round I removed them and stuck the pipe from the spray up inside, yes I got showered again lol. But this time I saw some black residue coming out, Not a lot, but it was there.
The subject of the fuel filter was brought up and yes fuel flows through it without issues. I`ve got into the habit of checking it regularly.
I`ve had the coils including the carrier out of the frame. I stripped everything and put in new bolts to make sure everything is earthed as it should be. I also used a meter to check the voltage at the coils as I have been considering a relay bypass. I am dropping only 1 volt through the harness compared to what the battery holds.
One of the things that was thrown into the mix by the previous owner heavily steers us to believing that the carbs are in fact the issue. Just got to find out for sure.


Mike

JustMike
Forum Regular
Forum Regular
Posts: 65
Joined: Fri Jul 20, 2018 7:14 pm
Location: Scotland
Location: Scotland

Re: Help needed. Do I have a carb problem ?

Post by JustMike »

Well I gave the carbs a good wash out and a blow dry with the compressor.
Found some flecks of dirt but not enough to make me think they would cause a problem.
Interestingly when I flushed the air mixture screw holes the cleaner did come out black for a second or 2.
I looked up inside the jets and their relevant orifices with my inspection camera and everything looks clean.
I checked all the float levels and got some interesting measurements. No1 - 17 1/2mm. No 2 - 15 1/2mm. No3 - 16 1/2mm. No4 - 15 1/2mm. No5 - 17mm. No6 - 16mm.
Would these settings not cause the bike to run lean though ? Bearing in mind that revving from tickover in neutral I get some black smoke from the exhaust, and the end of the can is black with soot.
They are now all set at 15 1/2mm.
I have also set the air screws at 2 turns as a starting point. They were at 2 1/2 turns.
While I`m in there I am replacing the inlet manifold rubbers, just in case.

Mike

User avatar
Goss
Forum Regular
Forum Regular
Posts: 159
Joined: Tue Jun 30, 2009 8:13 am
Location: West Sussex, England
Location: West Sussex, England
Contact:

Re: Help needed. Do I have a carb problem ?

Post by Goss »

Sorry, I haven't been on here since July, my bad! I rebuilt these carbs for Mike Ire***d three years ago, he fitted the carbs and they fired right up then did 30-50 miles on the bike but due to lack of use and a hankering for the latest bike traded his CBX in to the dealer as a part exchange so the dealer has had this bike standing for a couple of years.

Good speaking to you Mike, I will send you a replacement gasket and set of float bowl screws free of charge but would suggest sending me the carbs so I can test them to eliminate them from the symptoms you have described, you pay postage both ways. It does seem odd that they tickover perfectly at 1,000 rpm yet you are having all of these problems, can't understand why if they are dirty inside these tiny passages are all still clean? Seeing as the dealers expert has removed them and tinkered with them too I would suggest emailing me a photo of the float needles as I hope they were not leaking from standing so long and he has swapped them out for nasty fakes, I replaced them on the rebuild for genuine ones from Keihin.

Hope to hear from you soon.

Regards

Steve
Onboard http://www.youtube.com/watch?v=EqWSsdKtd64
Bike http://www.youtube.com/watch?v=ofjFhEd3

steve murdoch icoa #5322
ICOA Member
ICOA Member
Posts: 4069
Joined: Tue Mar 04, 2003 9:12 am
Location: St. Catharines, On. Canada
Location: St. Catharines, On. Canada

Re: Help needed. Do I have a carb problem ?

Post by steve murdoch icoa #5322 »

Can't beat follow-up service like that.
Good on ya, Goss.

JustMike
Forum Regular
Forum Regular
Posts: 65
Joined: Fri Jul 20, 2018 7:14 pm
Location: Scotland
Location: Scotland

Re: Help needed. Do I have a carb problem ?

Post by JustMike »

Hi Steve yes it was great to speak with you. I have not forgotten your kind offer to test the carbs.
I have ordered new manifold rubbers which I hope to get tomorrow and I will be doing a leak test like you suggested and then I will try the carbs on the bike.
Hopefully I do have the floats all set correctly as it is the first time I have ever actually done that. But I double checked measurements before and after so I`m sure they are now correct.
The float needles are zinc coated and the tops are gloss black, but not sure what type of material.
I will take a photo and send it to you so you can check if they are what you put in.
The look like the one in this link, inc the little "ears" on the wire clip. https://www.ebay.co.uk/itm/GENUINE-KEIH ... 1690426841
Yes Steve Murdoch, impressive indeed.

Mike

User avatar
Goss
Forum Regular
Forum Regular
Posts: 159
Joined: Tue Jun 30, 2009 8:13 am
Location: West Sussex, England
Location: West Sussex, England
Contact:

Re: Help needed. Do I have a carb problem ?

Post by Goss »

Thanks Steve, nothing worse than a new owner struggling with a good clean bike especially when purchased from a dealer.

Mike, it sounds like they have swapped out the original valves, the Keihin ones are not plated, lighter and viton tipped. Had they just cleaned them up your float levels would be correct I will send you a photo of the originals next to poor quality ones. I would expect yours to hold for a few months if that then leak badly.

Regards

Steve
Onboard http://www.youtube.com/watch?v=EqWSsdKtd64
Bike http://www.youtube.com/watch?v=ofjFhEd3

JustMike
Forum Regular
Forum Regular
Posts: 65
Joined: Fri Jul 20, 2018 7:14 pm
Location: Scotland
Location: Scotland

Re: Help needed. Do I have a carb problem ?

Post by JustMike »

Its funny that you say that about the float levels Steve, that thought went through my head.
But no information has been forthcoming about whats been done to the carbs. And as you said there are lots of fake parts out there and I have no idea what I`ve got.
I have a few times fouled a plug when starting from cold. Maybe leaking valves are the cause. And I`ve also had fuel come out of the bowl over flow pipes when sat overnight.
This is why I hate other people working on my bikes. I like to know whats been done to them.
I`ve uploaded a photo of one of the float valves for you Steve. Also that seal has come back to its original size which was suggested above would happen.
Steve if you think I have fake float valves, can you send me a link for genuine ones so that I can get them changed ?
I`m off to scavenge the net for more info lol.

Mike

PS.
Just figured out how to load photos properly lol.

7715

7716

JustMike
Forum Regular
Forum Regular
Posts: 65
Joined: Fri Jul 20, 2018 7:14 pm
Location: Scotland
Location: Scotland

Re: Help needed. Do I have a carb problem ?

Post by JustMike »

Steve I double checked those valves.
They are I believe made of aluminium and not zinc plated as I first mentioned.
I also come across a post showing genuine Honda valves alongside fake ones which implies my ones are genuine.

Mike

daves79x
ICOA Technical Director
ICOA Technical Director
Posts: 4738
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA
Location: Knox, PA

Re: Help needed. Do I have a carb problem ?

Post by daves79x »

They look like Keihin valves.

Dave

JustMike
Forum Regular
Forum Regular
Posts: 65
Joined: Fri Jul 20, 2018 7:14 pm
Location: Scotland
Location: Scotland

Re: Help needed. Do I have a carb problem ?

Post by JustMike »

I found a photo Dave, then lost it again, showing genuine against fake valves which implied that as you say they look genuine.
Tomorrow I`ll be doing some final checking of passageways etc before doing leak tests etc.
But it niggles me that I`ve seen evidence of fuel leaking from a couple of the bowls so I think I`ll also check out the overflow pipes in case any are split.
Better to check them now while the carbs are out.

Mike

User avatar
Goss
Forum Regular
Forum Regular
Posts: 159
Joined: Tue Jun 30, 2009 8:13 am
Location: West Sussex, England
Location: West Sussex, England
Contact:

Re: Help needed. Do I have a carb problem ?

Post by Goss »

They certainly are the genuine valves that I supplied and fitted which is great news, looking at the photos you sent there should be no partial blockages on any of the jets they need to be completely clear. Check the air bleeds in the top of the carbs are all clear too as old fuel can easily block the one under the black banana shaped cover. Sounds like your stand pipe has cracked so best to clean them thoroughly and solder them, too much heat will make this harder to solder.

Let me know how you get on Mike.

Regards

Steve
Onboard http://www.youtube.com/watch?v=EqWSsdKtd64
Bike http://www.youtube.com/watch?v=ofjFhEd3

Post Reply

Return to “CARBS: Cleaning, Rebuilding, Swaps, Aftermarket, Tuning, Syncing, and More”