Topic: CB750 K2: Engine not running smoothly at higher speeds

[CB750F2]

Recently I fitted a new set of aftermarket points to my F2. The bike ran fine for about 20k and then lost power and I struggled home on probably only two cylinders. I found the problem to be a loose rivet on one set of points. This rivet connected the spring arm to the moving contact. This can easily be checked  by disconnecting the blue and yellow wires from their respective points and measure the contact resistance with a digital multimeter. There should be almost zero resistance with the points closed. Wriggle the spring arm while reading the meter - the reading shouldn't change. If in doubt remove the points for a close inspection. In my case I was able to tighten the rivet and the bike is running fine again. I have also ordered a set of Hitachi points from Z1 Enterprises. Why did I purchase aftermarket points you may ask? It was because the local Honda dealer quoted me $75.00 for one set of genuine points and $13.00 for aftermarket - I thought it was worth the risk.
         I am not saying that this is your problem but it is easy to check.
Regards Pat

[Terry in Australia]

Geez Pat, I've got a few sets of new OEM Honda points sitting in a box somewhere, I'm gonna have to put 'em on EBay! Cheers, Terry.

[Miob]

I took the bike for a ride tonight. She behaved very well


Thanks for all the tips. I'll just need to wait till the problem comes back and then I can check all the things that have been mentioned in this topic.

[CB750F2]

Yes Terry and I wasn't joking! Pat

[phil71]

Terry, of course there's a right way to use inline filters, but you're assuming the petcock is alright, and it doesn't sound like it is, and he's not yet checked it. I wasn't blaming filters per-se, but whenever i see them on a recent purchase, I can expect a tank or petcock issue created the need for them. It's rarely ever just some knowledgeable guy who likes redundancy, but more like a tank whose innards resemble the titanic.

[Miob]

Sorry, I should have said: But I had already checked the tank before I ever tested the bike, it looks like new inside. But I have not opened the petcock yet, will do that this weekend.

[Terry in Australia]

Terry, of course there's a right way to use inline filters, but you're assuming the petcock is alright, and it doesn't sound like it is, and he's not yet checked it. I wasn't blaming filters per-se, but whenever i see them on a recent purchase, I can expect a tank or petcock issue created the need for them. It's rarely ever just some knowledgeable guy who likes redundancy, but more like a tank whose innards resemble the titanic.

Thanks Phil, of course I don't assume that I can speak for the majority of bikers, but as I said before your Straw Man "Stoned Tiger" response, I've been using inline filters on just about every bike I've owned (with the exception of the 3 fuel injected bikes with their superior filters) for the last 30 years or so, because I don't think the OEM mesh filters fitted to older jap bikes are adequate. Cheers, Terry.  

[Miob]

A little update:

After doing the things I already described in this thread and a small adjustment to the exaust (meant to make it a bit less loud. Works very well I have to say), the bike has been running great. So far the problem has not occured again. Yet.


One point for the airflow guys: I tried it out a bit and (honestly to my surprise) and you have a very valid point. If I move my legs to act as an airbrake, the bike immediately starts running rough. Thanks for the tip. I might make new filters or experiment a bit with a shield.

[robvangulik]

I know for a fact there are quite a number of CB riders living near you, you could become a member of the Dutch CBFourclub. There is a lot of knowledge and also a lot of parts going around there.....

[Miob]

I know for a fact there are quite a number of CB riders living near you, you could become a member of the Dutch CBFourclub. There is a lot of knowledge and also a lot of parts going around there.....

Yes, I know and I have considered it.

But, I am a student. If I want to ride bikes I really, really have to count every penny. I know membership is not expensive, but that also counts for the membership for them BMW-R club, for hosting your own website, for a real Flickr/photobucket account etc... etc...

Before you know it, you've spend hundreds of euro's .

When I finish this study and find a job, I will.

[robvangulik]

I'll keep an eye on you anyway, already bumped into you several times, in Achterveld for instance

[Miob]

Achterveld is always fun! Say hi next time