I have a 1991 CBR1000FM that’s been in the garage for 5 years without being used. It’s still in really good condition (thanks Honda) and starts well with choke. However….it won’t run without choke even when warmed up, and dies if I try to open the throttle. Here’s the stupid bit – it was stood for the 5 years with fuel in the tank! {I promise I won’t do that again}. I’ve drained the tank and float chambers and put fresh fuel in. But the problem persists. Having looked around this forum, I’m thinking it’s clogged jets (idle and/or main) as there’s a pretty good spark at the plugs and so the electrics seem sound. First question, therefore, is – is it indeed likely to be clogged jets? If so, I’m reluctant to open up, clean and rebalance the 4 carbs myself and if that was the only solution I’d probably pay to have that done professionally. But I’ve read quite a lot of good reports about Seafoam (other similar products are available) and thought that might be an option. I’m thinking of putting it into the fuel tank as a 50:50 mix and running it for a few minutes before letting it soak for 24 hours, and maybe doing the same a second time if necessary, but NOT spraying it directly into the carbs. So the second question is – if I did that, would the Seafoam actually reach the jets and unclog them (assuming of course, it is indeed the jets that are the problem) and hence avoid me having to have the carburettors completely dismantled etc? I guess it's worth a try anyway, but I'm looking for guidance on how likely I am to avoid having to take the bike to a garage. Any views would be appreciated. Whatever happens, it's been a "good (albeit potentially costly) lesson" for me.

 

I don't want to be the bearer of bad news but Sea Foam will not fix a pilot circuit problem. I'm not saying this because I'm an expert but personal experience has shown me there is no amount of Sea Foam you can introduce to your carburetor that will fix your idle and "have to have the choke on" problem.

That being said, all you have to do is clean your idle jets. That's it. You do not need to rebalance or touch any adjustment screw if it worked fine before. Yes you can go by the book but in my opinion it is not necessary. So if you have to pay someone to take the carbs out, just have them cleaned. If you can do that yourself you would be screaming down the pavement already lol!!!

 

I read further into your post and notice the word dismantled. The float bowls come off, nothing more. And make sure the plungers slide ok. If your problem is not solved after that you will definitely be travelling down the "road" lol!!!

I think you're good though - Clean the pilot jets

 

GronkFries, thanks for your "encouragement" - even if the thought of me taking the carbs into my own hands is just a little scary. I'd be happier if it were a single carb lawnmower. Let's hope my CBR1000 doesn't end up being just that! So you do think it's a jet problem. And if I understand you correctly, both the idle and main jets are accessed by removing the float bowl chamber. Would I need to fit replacement O rings once I've split the float chamber from the carb body or should I be able to reuse the current ones, and are there any other replacement parts I'd need when reassembling? The reason I ask this apparently trivial question is that I'm actually in France and so getting spares of any description is frankly slightly more complicated than just "going down the road" to the English/US dealer. Would Seafoam be suitable to clean the carb components or would I need something else? You mention "plungers". Apologies for the dumb question, but what do you mean, and are they too accessible once the float bowl chamber is removed? Hope you don't mind all these stupid questions but I'm trying to get my head clear about all this "obvious" stuff before leaping into the abyss. If there's anyone else out there who can offer some advice (short of actually holding my hand when I pick up the screwdriver) I'd welcome anything.

 

The topic of Seafoam and its merits is pretty well covered in tons of threads here. Some people love it, others think it's snake oil. My personal opinion is it's a good additive to use on a regular basis. I'm not sure how great of a thing it is for corrective maintenance. At the end of the day you will have to be the judge.


If the bike has sat for 5 years, a deep clean of the carbs is probably in order. Looking through the threads on here where people have had similar situations as you, they try doing a little bit, but not all of it. More often than not, they pull the carbs repeatedly until they get it right. They would have spent less time and effort jumping in head first and cleaning everything the 1st time.


I will admit that there seems to be a fair amount of voodoo in working with multi-carb situations. But in reality, it's not bad if you take your time and have the right tools.
Buying the proper tools will cost you about 1/2 of what taking it to a dealership will cost you. Some of the tools are specialty items that you may not have a use for outside of carb work. There are probably independent mechanics in your area that can do it cheaper. But if you have a decent work area, some time and patience, you will find that you will get a lot of help and coaching on here.

 

I've been looking at various "how to" videos. Now understand what "plungers" are (Dahhh), but many of the videos go into what seems to be a much deeper clean by removing the diaphragms and basically anything that is removable and cleaning it all. Gronkfries suggested cleaning just the pilot jet as being the most likely problem. I guess it's probably best to do everything once the carbs are off, but is it really necessary as for a novice like me, that adds to the likelihood of cocking it up somewhere along the way?

 

It's up to you but I believe you will discover is that the rest of the carb system needs cleaning also. Five years of fuel sitting is a guarantee for clogged jets and passageways.
The bike may run without doing it but I doubt it will perform to its potential. These bikes are incredibly hardy pieces of machinery but they are very finicky when it comes to the fuel system.

 

It's your idle jets for sure - I've cleaned mine a dozen times over the last 5 years. It seems about 3 weeks is as long as I can let my bike sit before they get clogged.

The first time you do it, it will take a couple of hours. But you can get it down to 25min once you're familier with the process.

1. Take the tank off.
2. loosen the rubber seals between the carb stack and the head, and the carb stack and the airbox.
3. remove the two bolts holding the airbox to the frame and slide it back an inch.
4. take off the PCV vaccum hose from the top of the carb

now you should be able to pull the carbs off the head, and flip them upside down - you'll loose a little fuel in the process but no matter.

5. take off the bowls, pull the idle jet (the one which requires a socket, not the one in the centre with the flat screwdriver end) and use one strand unwound from a piece of picture-hanging wire to clean it out.

You should be able to see through it when it's clean - it's a tiny, tiny hole though.

reassemble in the reverse order and you should be golden.

One trick I learnt is that if the idle is lumpy, and you suspect a bad jet, you can spray water on the downpipes immediately after starting the bike. If the jet is clear, that pipe will get hot really quickly, if it's blocked, the pipe will stay cold.

That way you can tell which jets need attention.

 

I like this thread! Agree with Hamlin you can clean it thoroughly, take it all apart, use a guitar high E string, Pine Sol, etc. I actually did all that with a CB650C carb bank and it runs sweet, started up immediately and idles fine. Smells like a janitor's closet but who cares... You shouldn't separate the carbs though, unless a smarter person here thinks you should and with proper direction. Full cleaning is always the recommended way.

Rockpool, I think your suggestion is fair as well - that is what I would do with a bike that has recent usage. A past GF had a VStar that required the 'ol idle/pilot cleaning every spring. I tried everything including the Sea Foam drench and still had to get it on with those carbs regularly. One day I hope to have lots of money and stick with fuel injection - People are even patenting CV slide throttle body injection adapters, but way too pricey currently.

KMCBR1000FM, I would like to add that I don't always work on everything I own all the time. Once in a while I pay the freight and have someone take care if it for me. For example the GoldWing I drove down to Florida last fall is coming home in a few weeks and it needs a fork seal replaced - Someone is going to take that to a shop and get it fixed before I fly down there. Maybe you could have someone do your carbs for you, no shame in that

 

Gronk is wise, (except his choice of NFL teams),
if corrective maintenance isn't your thing, there is absolutely nothing wrong with taking you steed into a shop. Just spend some time and find a reputable place.