90 hp honda carbs

Ok Ive got this 90 hp Honda and I had posted a previous thread about my carb issues , it doesnt seem to be sucking through the carbs . If you place your hand over the carb at idle there seems to be no sucktion on the bottom carbs , the top 2 are the only ones that seem to be doing anything , now Ive had these carbs off 5 times , changed the coils around , changed leads , changed plugs , reset the valves . Just outta ideas now , somebody did mention balancing the carbs , how is this done ? Help

The first thing i`d suggest is to do a compression test on all the cylinders to ensure they`re more or less equal. Once this has been done and if they checkout ok then move on to checking you have a spark at the plugs.

As you say you`ve cleaned the carbs 5 times then have you replaced the gasket between the carb manifold and cylinder block or just reused the old one as it looked ok? If it`s not been replaced then it needs to be. If it has been then try starting the engine and carefully spray a little engine cold start, easy start, fast start or similar around the manifold gasket and see if the lower cylinders kick in. If they do then you`ll know you have a leak which will mean that air is being drawn into your engine via the leak rather than through the carbs.

A word of warning.... Be VERY careful when using these products as they`re contents are HIGHLY inflammable!

Hopefully this will give you a start of where to go now. If no success with any of this then post up a reply and i`ll explain how carb balancing is done.

Cheers, Matt.

Thanks Matt , the compression is good , does the long thin jet with the oring actually have a small hole throught it or does the fuel flow through the side holes ? Im gonna change out the jets and gskt and see what happens . Im interested in balancing these carbs so any advise would be appreciated .

Hi, the jet should your describing is actually a tube with several holes down it`s sides so yes it should be open at both ends. These tubes often develop hairline cracks in them and can cause your fuel deliver to go all over the place instead of where it should be and at the flow rate required. If the jets are removed then new "O" rings must be fitted and great care must be taken when fitting them to avoid them being nipped or torn.

I`m not long back from work and it`s 2am in the morning so i`m off to my bed but i`ll post up about carb balancing and hopefully find a link to a decent video showing how it`s done. I was a motorbike mechanic for over 30yrs and have balance thousands of carbs in my time so i`ve got a fair idea of how it done lol.

Cheers, Matt.

Ok, I`m alive again and have come up with a link that explains things clearly in regards to carb balancing. I actually use the balancers shown and can honestly say they`re very good and have used them on both my BF 50`s and my BF25. Have a hunt around the site as it has a detail explination of how to both setup carb balancers themselves and then how to use them correctly. The principle is the same for both mercury and dial gauges but i find these ones with stainless steel rods far easier and i`ve yet to break them unlike an old dail set i had.

http://www.carbtune.com/

I can`t remember if it`s the 5 or 6mm adapter that you need to screw into the carb manifold but you`d soon see when the small philips head screws are removed. The balance adjustment screws are the ones with the springs around them with the blob of yellow locked on them. Go easy with adjusting these screws and just move an 1/8th of a turn at a time either way as that`ll make a big difference.

Hopefully this`ll give you an insight into the black art of carb tuning and if you buy a set of your own then they`ll pay for themselves in no time both by working on your own engine and then in beers from your pals who need they`re carbs balanced. The good thing is unlike motorbikes then you don`t have to muck about removing seats and tanks. It`s just hood off, screws out, adapters in and your ready to go.

Cheers, Matt.

Yipee I finally changed out the jets and bang she purrs like a kitten , Ive got a buddy whos going to balance them tmr so I should be fishing by midday . Thanks for all the help and Im ordering that tool on Monday .

Great to hear and hopefully you`ll have more success with your fishing than i had last month as all i caught was a cold lol. Best thing to do if you can is to drain your carbs down after each trip as it`ll reduce the chances of them getting gummed up again as they`re prone to do due to the modern fuel additives.

I actually work in a place where we build fuel dispencers and for bio fuels then they have to have special rubber seals so it`s best to avoid bio fuels if you can as it won`t do the standard carb rubbers seals any good.

Once you get your head around how to balance the carbs then you`ll soon see how easy it is and start to wonder how places can charge so much for something so easy. Even if you just did it for your pals for beer then you`d soon need a bigger fridge.

Smile be happy, Matt.