Most motorcycle problems are caused by the nut that connects the handlebars to the saddle.

No power up the rev counter

Share
avatar
liverpool_f_
the 900
the 900

Posts : 368

No power up the rev counter

Post by liverpool_f_ on Wed 15 Oct 2014, 3:58 pm

Hello all,

I am loving my cb and this forum but I have recently run into an issue which is keeping the bike off the road. During city riding it feels pretty normal but once you open the throttle and get up the rev counter the power delivery is very jerky and there is a serious lack of power.

The bike has done 55k and has no service history which is a good start. Since I bought it, it has had new oil + filter, air filter, sparks and coolant flush. The sparks that came out of it were horrible but the new ones didn't sole the problem. This issue is new and wasn't present in the first few months I owned the bike. I am certain it will need the valve clearances done but that is one for my mechanic when I get a bike more cash. I am going to clean the fuel strainer next but my thoughts after that start getting more expensive. I was looking at replacing the coils but they are fairly expensive if i am not sure that they are the culprits. Maybe a vacuum leak somewhere?

Any suggestions would be muchly appreciated!
avatar
HomeBrew
the 900
the 900

Posts : 470

Re: No power up the rev counter

Post by HomeBrew on Wed 15 Oct 2014, 6:12 pm

I agree that replacing coils just for the hell of it seems like an expensive experiment. You could check for vacuum leaks by spraying ether or gas around and seeing if it affects the engine speed. Have you tried this website? http://www.themotorcyclemedic.com/bd-1.html it has some ideas for things to test if you click "the bike died on me". and then check air talks about vacuum leaks.
avatar
eternally_troubled
Admin
Admin

Awesome!
Posts : 3694
Location : 'ere be fens. (near Cambridge)

Re: No power up the rev counter

Post by eternally_troubled on Thu 16 Oct 2014, 11:52 am

You should check (off the top of my head):

* When the problem occurs, pull over (where safe) and open the fuel tank - if there is a 'hissing' as you open the tank it suggests that a vacuum is being created in the tank, which suggests the tank breather is blocked

* That the vacuum pipe to from the inlet manifold to the fuel tap (on the LHS of the bike under the edge of the tank near the fuel tap) is not brittle, crazed or otherwise buggered. If this pipe does not seal the vacuum is not applied correctly to the fuel tap and the fuel tap might be partly off - this might not show up at slow speeds but would if you get going.

Anyway, good luck finding the problem.
avatar
liverpool_f_
the 900
the 900

Posts : 368

Re: No power up the rev counter

Post by liverpool_f_ on Fri 17 Oct 2014, 3:20 pm

Thanks for the suggestions guys. The breather is fine. I had the tank off last weekend and checked it wasn't blocked. I will replace the fuel  tap breather hose as a matter of course but the old one doesn't look too bad. Any other thoughts if this doesn't rectify the problem?
avatar
jonny10
the 900
the 900

Awesome!
Posts : 301

Re: No power up the rev counter

Post by jonny10 on Fri 17 Oct 2014, 8:27 pm

Has to be either fuel/air related or electrical
If the tests suggested by Homebrew & Eternally check out then I'd be thinking carbs. If she's runnin ok at low revs/speeds then maybe the main jet could be dirty.  Clean the carbs out and make sure all airways are clear.  Might want to check the fuel tap filter when you're at it.

If you've checked the condition of HT leads & caps (handy way is spray some water mist on them in the dark and see if there's any spark leak) and these are ok, then, I'd say look at the coils. Before you do spend big, get them tested by a bike shop or auto spark, shouldn't cost much to get that done. Or, if you can get a multimeter you can do it yourself - youtube has vids on it.
avatar
Llewelyn1965
the 900
the 900

Posts : 344
Location : Swansea

Re: No power up the rev counter

Post by Llewelyn1965 on Sat 18 Oct 2014, 2:32 am

As above, but be aware that when checking the coils and HT leads with a multimeter, .....it can lie( the barsteward!!!) I have tested my coils and HT leads off the bike and they showed as the Haynes manual said, but after much checking/testing/guessing decided to change the coils and HT leads which resulted in the girl working. As suggested by a friend might be the problem, the coils or HT leads were working fine when not doing anything, but when under load-IE actually working, they were breaking down.
avatar
jonnytub
Hyper Viper
Hyper Viper

Posts : 49

Re: No power up the rev counter

Post by jonnytub on Sat 03 Jan 2015, 7:51 pm

Just another thought on the breather hose and or other hoses, is it possible that you've pulled the hoses out to check for blockage and put them back where you found them?  Done the same thing on an old bike with the same problem, turns out the way they went back in was kinking the hose (caused by debris buildup or in my case a large stone which turned the breather hose a further 45 degrees).  Would never have known the problem stemmed from there as the place it kinked was behind the rear lower plastics.

It was only after consulting the manual for the proper breather hose route did I find it. (my bike was out of action for a month!)

Sponsored content

Re: No power up the rev counter

Post by Sponsored content


    Current date/time is Sat 18 Nov 2017, 8:36 am