White Bros cam swap

[scottly]

I just finished replacing the stock FT cam with a White Bros WBX-1 cam. Releasing the chain tension is a pain, and the manual is of little help. I found I could push the A wedge up with a screwdriver while depressing the B wedge with my other hand far enough to clamp a vise-grip onto the A wedge.
The cam specs, according to a copy of a W-B catalog I found online are:
intake lift .360" exhaust lift .360" intake duration 258* exhaust duration 258*
Since this cam came from an XR, it lacks the tach drive pin, unlike the WBX-1FT version, so I used the plug from the XR to seal the hole from the no longer needed tach drive. (BTW, the drive and cable weigh over 1/2 pound!)
My initial impression is that it's running a bit softer at lower revs, then comes on stronger as the revs increase. I suspect I will need to go to a bigger main jet, as it was still on the lean side with a 185 before the cam change.

[WTF304]

Maybe it's not the jets ..... could it be the carb doesn't have enough CFM and fuel flow to support the demand ? I thought about a different carb but I'm not 100% sure whats going to be a good fitment. I'd like to get my hands on a flat slide but thought about a carb that's a little more like the stocker. A Mojave has a cv style carb but the slide is flat towards the ends and round in the center ... if my mental picture is right. Going to hit up a local yard, check the bikes laying around there and get some better idea's of what machines had what and possible compatibility.

[triguyracer]

Have you checked your cam timeing with a degree wheel,a few degrees can make a big diff in how crisp a motor is and how well it responds,Dont know if White Brothers on anyone else these days sells a slotted cam gear for a ft or xr though I would think that one could be found .Sounds right about going bigger on the main jet.I was supprised how many sizes I had to go up just to get good performance with just a pipe and getting rid of the air box with the stock carb and stock motor,but now I got it jeted good I am very pleased with how well the stock carb is working,I had my doubts about making a cv carb work as well as I have this one working 

[scottly]

The dyno test with the new cam showed the bike to be lean, as I expected, so I started increasing the main jet from 185 until I stopped at 198, as it was having little effect. The blue curve is with the new cam and a 198, and the red curve is with the stock cam and a 185 main. I pulled the carb today, and found that the needle jet, even with the needle shimmed .046, would only flow about the same as a 182 main, which explains why increasing the jet size had so little effect. I've drilled the needle jet to about .106" from the stock .101", so this should allow enough fuel to support the 198.

[WTF304]

Looks good on paper .... RPM went further and didn't fall flat. Lost a little torque but you did gain more HP. Is it still possible to pick up the bigger carb that was once offered ? .... you could get a carb from a different honda of that era, regardless if it's 4 in a row, you could modify one of them .... cut down the butterfly rod and block off the side's that supply fuel to the other carbs in the system. It's sounds like alot of work ... and you probably won't have the accelerator pump. You could also bend the pump linkage arm a little so the pump will work more fuel to the carb, i did that once to a stock carb on my other FT and i was surprised but it did seem to do alot for me.

[scottly]

Look at the difference at about 2650 RPM: The WB cam made about 8 more ft/lbs of torque, and about 4.5 more HP.

[scottly]

The stock cam specs, from what I've gathered from published specs and comparing to the WB cam are:
Intake duration 254*, .330" lift (at valve, zero clearance)
Exhaust duration 248*, .325" lift