Lewis' XJ750 Cafe Racer Project

I've been doing this project for a few weeks now, and I think it's finally time to start a build thread here.

Similar to Skylrk62 I'm documenting the build on Youtube, you can find my playlist here: http://www.youtube.com/playlist?list=PL ... xYdEgzEvRu

Yesterday I got her running and look what happened http://www.youtube.com/watch?v=Ru_8cY4eqYE

I have cleaned the carbs but messed about with the float height and I think the butterflies are opened too much (How do you bench sync it when there are only 3 adjustments for 4 carbs?)

The problem I have now is the bike is idling really high, the tach isn't working but I think it's idling around 4,500rpm right now, and to be honest it's so loud it hurts.

I think if I just close the butterflies up fully and then open them up a 1/3 turn it might idle low enough for me to be able to put her in gear to test the gear box out.

I've tried turning the pilot/idle adjuster but I can't tell if it's idling higher or lower, and I can only run the engine for about 3 seconds at a time (straight through pipes)

I don't see any gaps in the boots around the carb inlets and outlets, one of the diaphragm cover screws can't be used because I was drilling a seized screw without a head after a long day and didn't drill straight. It has been filled up with chemical metal and so has the edges of the cover just in case, but the slide does return freely and as far as I can tell it's not leaking, I can't do a soapy water test at the moment because the bike really is so loud. (It's got a mind of it's own, I bolted a baffle in and somehow it undid the bolt and nut and shot the baffle out a few metres behind it).

After I can get it to idle low enough and check the gearbox (At the moment it won't shift higher than 3rd gear, but my other bike won't go higher than 2nd gear without running though it has a PNF)

After that it should be down to a full strip, design all the fibre glass (Or possibly carbon fibre) bits I'm doing and get each part cleaned up and painted.

One of the stanchions on the forks is so badly pitted I'm going to have to have to replace it (Not getting it rechromed) so I was thinking of dropping in a more modern front end, like an 04 R6 or something, so I'll have to get through that whole issue fairly soon.

I have about £450 left to spend on this bike.

 

Bench Sync Your Carbs

The idle mixture screws do not adjust idle speed. Set them at 2 - 2.5 turns out to get the A/F ratio in the ballpark without going too lean. Idle speed is changed by the knob that sits between the #2 and #3 float bowls (Look below the intake boots, and above the starter, you'll see it peeking out).

To do a running synch match #1 and #2, then match #4 to #3, finally match the 1+2 pair to the 3+4 pair. #3 is the "master" of them all, which is why it gets the idle speed adjustment screw instead of a synch adjustment screw.

You won't need to have the bike running to see if the shift mechanism will engage all of the gears. Turn the rear wheel slightly as you move the gear lever by hand. That will allow you to check the shifting assembly, and for gear engagement.

If you run out of budget for the front end swap you can VIGOROUSLY clean and degrease the pits on your current forks and fill them with a 2 part, metal filled, epoxy. heat cure the epoxy with a shop lamp, and then wet sand the epoxy until it's smooth and flush with the fork leg. That, along with new seals, will get you by for a long while.

 

Thanks for the reply, I did mean the idle knob, I was turning it but didn't notice any change in engine speed, do you know which way it needs to be turned to idle slower?

I will be getting a double vacuum gauge soon but I need to get the idle down first.

It's good to know about the master carb, I never knew of that, but how do I adjust the butterflies with it? There must be some way to otherwise carb 3 would be out of sync when the compression of the cylinder is different to the others. Thanks for the gearbox advice too, I will go outside in the rain now and try it.

I think I should be able to meet the budget with the suspension, it is possible to pickup a front end for about £180 The bit I was worried about is actually getting it to fit in, and having to pay a machinist for whatever work they have to do.

All else I will have to do is pay for:

pod filters (Almost impossible to tune on this bike I've heard?)
fibreglass kit's
Speedo and tach
lights and indicators
clip on handlebars
new drum shoe
paint
seat upholster (if I screw it up)

and then tyres, MOT and Road Duty. - But I'm not including those in my budget.

 

Cat food in the exhaust?!

 

It sure was, almost threw up picking it up.

 

Dang squirrels or chipmunks. Others have had similar problems. One guy had acorns in his exhaust that blew out and hit his leg, ouch!

 

I'm guessing that you don't have kids. Cat food is not nearly as icky as other things I've had to pick up.

 

You bench sync the butterfly for #3 using the idle speed knob.

 

That depends. Used cat food pretty much equals anything kids produce.

 

Not even close. Ever get somebody else's puke in your mouth?

 

Whoa, k-moe rolls out the heavy artillery............

 

That should have been obvious to me!

Does anyone know which way you turn the knob to close the butterflies?

I really want to get this bike to idle properly, does anyone know anything else that I should do to bring the idle speed down? - there is slack in the cable.

I adjusted the float bowls to be open more, when the bike was running out of fuel it idled nicely, but I was wondering if I brought the bowl height down again there would be a lack of fuel at high throttle openings?

 

You turn the knob counter-clockwise... If I were you I would clean the carbs again. Make sure your choke slider isn't sticking too. I suggest reading this too http://xjbikes.com/Forums/viewtopic/t=14692.html it has so many tips, and it gives great advice on jetting the carbs.

 

Turns out the throttle cable was just too taught, she runs nicely now!

http://www.youtube.com/watch?v=HJ9vG0dpBdA

I'm building a workshop now so I can take her apart and get started on making some rear sets and taking the paint down.

 

I'd like to see how this is coming along.

 

I'm just finishing up on the foundations of my workshop, should start back on the project in a month, just looking at swapping the forks to the Maxims air forks.