[honda roffel]

bought an US CB 450 SCE nighthawk from 1986
don't know its history , don't know how long it stood still.
but started directly

great bike, love it but it has some problems.
the most annoying is that when accelerating in the range of 2000 > 4500 rpm it is holding back.
above that it works fine.

so with new spark plugs drove about 200 miles and stopt the bike with the emergency switch and toke out the spark plugs.
and this is how they looked like

a friend told me it looked like the bike was tuned to lean

thing that may influence all is that after about 40 miles i used a flued to mix with the petrol.
forté moto power 1 http://www.forte-nwe.com/SE/Forte+products/Fuel+System/Moto+Power+I.html
some details

Forté Moto Power I is a complex mixture of specially selected solvents combined with surface active substances and binding agents. It will dissolve built-up deposits in fuel systems. When used in accordance with directions in the tank of a motorcycle Forté Moto Power I offers the following advantages:

* Cleans the tank, fuel valve, carburettors and the complete injection system.
* Removes deposits from nozzles, metering nozzles and injector needles.
* Dissolves tar, lacquer and resin in the complete fuel system.
* Stabilises fuels mixed with alcohol.
* Neutralises acids generated by ageing and oxidation of the fuel.
* Lowers fuel consumption and improves engine performance

but today with a new run things did not seem to be better

if you look at the sparkplugs, what would you think about this?

 

[66Sprint]

You'd need a run with only gas.... Those do look a bit lean, but you'd have to be sure your carbs are clean (and the primary and secondary mains aren't swapped as well as look at their sizing) before any "chop test" would be valid.....

 

[honda roffel]

What i did was to give the carbs a treatment with the forté moto 1 mix

not one bottle in the tank, but mixing it whit 1 liter petrol.
took the hoose of the tank and put one of these (don't know how they call them)om top of it

started the bike and filled the carb with the mix i made.
let it run for a while and put the bike in the garage to let the mix soak a for the night.

build it up this morning but did not get the change to ride it again.
so have to wait and see if it works.

 

[honda roffel]

got to ride the bike the last days.
after the repair mix it drove a bit better, but i was unsure about it so the next day i went in the car to a repair shop to ask what the cost would be to clean and re tune the carbs.
after agreeing a price i got home to get the bike, and to my big, very big surprise the acceleration problem was gone :shock:
so i could cancel the carb tuning.

 

[66Sprint]

Well, you have demonstrated that the problem was likely in the midrange jetting in the carbs.....
I'd recommend a thorough carb cleaning anyway, even though it seems to have cleared up somewhat......

 

[CMHN]

I second that, adding carb cleaner to the gas is alright for light deposits, but if the bike has been sitting for a while there is going to be varnish and crud in those carbs. Your best bet would be to take the carbs off and give them a real good cleaning. Make sure every little hole is clear, it doesnt take much to gum up a carb.

 

[honda roffel]

i will clean the carbs later, i think coming winter.
are there some hint about losing the screws of the carb holders on the cylinder heads?
i think they have not bin loose for a long time.

 

[66Sprint]

impact driver.........

 

[honda roffel]

well the happy i was at first a week later i found out that the problem still existed.
so made an appointment with the bike shop and today they will clean and tune the carbs.

don't want to damage the engine driving with the wrong air/petrol mixture

 

[66Sprint]

I believe you could have done the carb cleaning/ adjustments yourself, but if you were in doubt, the correct thing to do is seek professional help....I hope they get your bike "squared away' and it runs well enough to meet your expectations... .....
As far as your English, You do better with it than I would ever be able to do with your native language......Keep us informed of your progress/results.... Steve

 

[honda roffel]

took a while , bike went to a shop, had to wait for carb service parts.
there was rust in the carbs, lots of gummed petrol.

was a big bag of money to get it working good again but it worked.

i only can say that this is a fine bike to ride, stearing is great.