TCI Question

[henri]

Hi,

I have posted a thread here before about my bike running lean or experiencing fuel starvation at high speed. Then I found my idling screw tips broke off in two of the carbs.

Ok all of that is fixed now and I am still experiencing the problem. I have balanced the carbs and set the mixture to a point where it idles with no problem. The trouble comes in when you open it up. It stutters and shoots blue flames (long angry ones) when I close the throttle.

Just to give you some background, the bike is a '78 XS special with the old style carbs with the brass idle screws, all stock jetting. A K&N filter inside the standard airbox and a four-in-one exhaust.

My question is, if I have a 4H0 (I think) TCI box with the vacuum advance connected, what will be the result? I bought the replacement TCI because the original was not working. And I read on the guy that rebuilt "Swamp Thing"'s website that the original used to be 2H7 and the 4H0 has the advance built into the TCI. That would mean that it is advancing the timing two times when under load or when does the advance start working. By the way, when exactly does the advance start to work. I can see the advance moving when I rev the bike up, but as soon as it starts moving the engine starts to misfire.

Thanks

[randy]

Uh, that would be me. Yes, you have too much advance. I'm not certain that it will solve your blue flame problem, but if you want to use the 4RO TCI, you should use the correct rotor from a 4RO bike.

[henri]

TCI Rotor

Hi Randy,

Thanks and sorry, I'm not good at names. Anyway, so I can't just unplug the vacuum advance?

So this means I will have to get the old one fixed or something and then reset the electronic timing. It is one step closer though.

Thanks very much.

[randy]

Just change the rotor and you will be OK. Get a rotor from an '81, that will match the 4RO TCI and correct the timing issue.

[henri]

81 Rotor

I wish it was that easy but it will in fact be better to fix the 2h7 TCI. I think its only re-soldering the joints. Over here XS11 parts are hard to come by.

Thanks for all that info on your website by the way, I had no clue the models had so many differences.

[mxmikie]

i have a 2h7 tci if you need one

[xs11lover]

Randy, I didn't think a bike that had a 2h7 box would run at all with a 4r0.....at least I didn't have any luck even getting it to start.

[cywelchjr]

Hi Randy,

Thanks and sorry, I'm not good at names. Anyway, so I can't just unplug the vacuum advance?

So this means I will have to get the old one fixed or something and then reset the electronic timing. It is one step closer though.

Thanks very much.

Or you could just tie down the advance weights on the existing rotor to let the electronic timing advance do it's thing. That would likely be the quickest fix, and should work just fine since the proper rotor has no cent advance on it.

[randy]

Tying down the weights will get him close, BUT, the 4RO rotor has a wider pointer, different dwell.

[Ivan]

Edit: Swapping parts to Africa may not be financially feasible.

I was gonna say tie the advance weights down, but someone beat me to it.

The 4R0 doesn't have anything to do with the vacuum, only the rpm advance. The 10M on the XJs has both vacuum and rpm advance in the unit and uses a vacuum sensor.

[henri]

New Rotor

Thanks guys for the help and the offer for replacement parts.

I have 2 2h7 TCI's and one of the later models which is now on the bike. One of the 2h7's is not working properly, and the other is on a xs 11 which I am busy with that I don't want to start hacking for parts.

As luck would have it I am in Johannesburg today and there is a second hand bike part shop here from where I get most of my parts.

What I would like to know (if I don't get a rotor) is if you could explain how the weights are tied down on the vacuum advance rotor. I don't want to go and break something.

Thanks again for all your help and advice.

[henri]

Rotor Weight tie down

Hi Randy,

Can you please explain what you mean by tying down the weights?

"Tying down the weights will get him close, BUT, the 4RO rotor has a wider pointer, different dwell."