Not really. The tach operates from the ground trigger on one of the 2 ignition coils, which does come from the CDI, but you can't decide the CDI is bad just because the tach isn't working. I suppose it's possible that the CDI is intermittently not firing the coil, but the tach did not 'burn out' the CDI. Hopefully they did a better diagnostic job than it sounds.. just from reading this I sense some guessing is going on.

If they happen to be correct, great. If not I would make them put the original CDI back in, refuse to pay for the part & diagnostic labor, and find another shop or tackle it yourself with help from here. They can't legally make you pay for a misdiagnosed repair that didn't fix the problem.. at least not here in the US.

 

My thoughts exactly about a lot of guessing going on, I wouldn't of thought they can try and charge me for misdiagnosed work in England either. The guy has supposedly got 25 years of experience, though from the sound of it, not in fixing bikes!!
Hopefully the CDI turns up today and fingers crossed it works, but I'm not gonna hold my breath on it.

 

Any update on this? I read this thread and thought OMG! Who is this guy you have working on your bike. You need someone that knows Hondas...not just motorcycles...yet you said he doesn't have any experience with motorcycles.

Takes a lot of year working on these things to understand them and a shop manual is a must...I would be moving the bike.

BTW, the low voltage on the battery that was cited earlier could shut the CDI down so I would question whether that is the problem. You need good battery to trouble shoot this properly.

 

Sorry haven't had internet for a while, to update the bike was fixed and it was the CDI, although I think it was more a lucky diagnosis. I have another question if anyone can help. my bike starts to sound louder when it goes over 5 and a half thousand revs, I thought it could be an exhaust valve issue, but have been told it is my cam tensioner sticking slightly. Any feedback would be appreciated. cheers Bill

 

Glad to hear the CDI took care of that issue. Much better alternative than having to fight with the shop over it being diagnosed incorrectly.

Can you describe the noise when you say it sounds louder? A light metallic rattle type noise possibly? There's a good chance it's the cam chain tensioner as it's a pretty common problem on the earlier CBR engines. Could also be loose valve clearances, but that would tend to make noise at all RPMs not just 5k to redline. However, if the valve clearances have not been checked it would be a good idea to do so anyway.

 

The bike does make the tell tale cam tensioner metallic ticking at low revs, but after 5k it sounds almost like a blowing exhaust although there is no lack of power.