Daed's Cafe XJ750

Hello everyone, bought a '81 XJ750 Seca a couple months ago and finally got it running right, into safe ride-able condition, and cosmetically in the ball park of where I want it to be. Everyone likes pictures, so I'll start with that.










And finally one to show where I tucked the electronics.


When I got it, it 'ran' but the throttle adjustment kept the throttle about 1/8 open to keep it running. So first goal was to get it running well. Checked clearances, cleaned the carbs, set floats, bench synced, running synced. Bam, running not too bad... but hot. Rejetted, runs even better and little cooler. Went to 41 on the pilots and 126 for mains. Might go just a tad bigger on the pilots still. Tried to colortune... but I'll go into that in my next post in this thread.

Here is a video of it running.
XJ750 Running


So no one has to mention it, I did check the rear pads. :wink:
I also had to repair the front right caliper which was seized, previous owner delivered it, by riding it, like that. Dunno how... was so tight you could barely push the bike... Rotor is fine though.


Cosmetics + electronics
Previous owner had started converting to a cafe racer but it was pretty rough. So I:
Made mounts for the seat.
Rewired a good bit of the bike.
Moved the ignition switch down to under the seat along with all the ECU and regulator.
Got rid of the giant old battery and built a tray for a nice new, super small lithium one.
Stripped off a lot of the old mounting points for stuff and cleaned up a lot of spots where stuff can been cut before.
New coat of paint to protect the frame.
Added a rear fender/guard.
Added some hyperlights and got rid of the insufficient brake and turn signals.
Made some new bars to raise them up about 2 inches to a more comfortable position.
While making the bars, I also made it easy to mount some bar end mirrors.
Make new stalks for the mirrors and mounted them on end of the bars.
Had to make a new brake cable, old one had too tight of a radius with the lower bars.
Added a tach and moved the speedometer a bit.
Cleaned up most of the overspray from previous owner and got some of the oxidation off some parts.

Plans for future.
I'll probably strip it down next spring, blast it and repaint most everything.
Need to add a better horn.
Might add an oil cooler.
Still have a few wiring issues to work out.
Frame needs work in a few spots.
Already replaced a lot of bolts, going to replace a lot more with new quality ones.
New tires in the spring as well.


I have some questions and some possible insights I came across while working on the bike, I'll post them next just to break stuff up a little.

 

So I tried to colortune, but I think my plug is messed up...
I get a bright blue spark but its up near the clear window, not down at the end of the electrode. At the electrode it only sometimes sparks and when it does is only a crappy faint yellow. So the bike barely runs when the colortune is in because one of the cylinders rarely fires... Am I doing something wrong or is the plug, which looks like it was made in the 50's, broken somehow? I checked continuity and resistance from the top of the electrode to where it should spark and there is almost no resistance at all. I'm not even sure how it is physically possible for the spark to short and jump almost half an inch instead of at the end of the electrode...


Something I found that I thought was very cool and may be a better way to bench sync than the 'stick a piece of paper in it' method. I tried the paper method and got it pretty close, close enough to run decently. I messed the sync up though while trying to do a running sync and ended up taking the carbs off again to bench sync to get it running again... :roll:
This time though instead of the paper wedge I opened the throttle all the way and used a caliper to measure from bottom of the throttle valve to the farthest point on the 'throat'. Wiggling the caliper to make sure it rests at the farthest point. Got all valves adjusted to within exactly 1/100 of an inch, let it close and they were all looked perfect. Put them back on the bike, blocked off the yics again and tested with my manometer and they were perfectly in sync!


I also had a question about air cooled temps if someone could answer. I've never owned anything air cooled.. It seems freakin hot! I used an IR thermometer to check the outside temps after raceing it around a bit. Before rejetting, the fins near the top of the engine would get up to around 320f and the 'indent' above the exhaust manifold area would get up to about 480f, the exhaust itself would go higher than the thermometer would read which i think is 650f. After rejetting, the engine temps seem to have come down about 30f on average, exhaust still off the chart, but that still seems really really hot. If it's that hot on the outside isn't it hotter on the inside and cooking my oil?

Thanks for any replies and thanks in general to the site, it has been an amazing resource so far!

 

Sounds to me like your colourtune plug may be fouled, might be worth getting some dyno time to set it up seeing as theres a lot of mods going on there. I'm unsure on the temperatures as I don't "do" imperial lol but that does sound pretty warm... Have you done a plug chop & what do they look like? Cooked white is lean, black powdery is rich & "strong cup of white tea" is spot-on
By the way, are those the Chinese Ebay shocks advertised for the 350LC? If so, how do you rate them? I was looking at them & they seemed a bargain at about £40 over here but I was unsure of quality (I've had some good stuff from China lately but their QC is still.... variable shall we say! )

 

The colortune looks like it has never been used before. I even took a little sand paper to the electrode end just to make sure there was no oxidation or corrosion of any type.

The plugs look alright, kind of a "nicely toasted marshmallow'' is the best way I would describe it.

Those shocks were on the bike when I got it so I'm not sure exactly what they are. They ride well, the only thing I can complain about them is that the 'connector' at the end of the rod is a fork type instead of an eyelete and that it is made out of rather soft aluminum. Previous owner had too small of a bolt running through it and it deformed the holes a little.

I'm also unsure of what the seat is off of. It does have 'Yamaha' in gold across the back, which is think is pretty slick. I'll have to put a picture up of the back.

:wink: 320f is 160c, 480f is about 250c, 650f is 340c

 

Hmm strange... for what they cost maybe you could try another colourtune? The plugs sound OK I guess, never toasted a marshmallow but I guess they go light brown lol. I wouldn't say 130-160c round the barrels was excessively hot for an air cooled bike that'd been ridden & then sat ticking over for a few minutes while you grabbed the thermometer, specially considering most watercooled stuff only just opens the thermostat at around 85c. I haven't got anything air cooled running at the moment or I'd check next time I rode

Yep, the shocks were (maybe are?) available on Ebay, they're usually listed for RD350LC's & I was toying with the idea of getting a set myself but wasn't sure what they performed like. Someone else is interested if they're any good as well, in the "some nice XJ900" thread.

 

I have no input other than I love the look so far. Hope you get it squared away mechanically!

 

I've just seen on the other thread (some nice XJ900) a link to the shocks on Ebay & it seems the kits now come with a selection of eyelet or forked end fittings. If you have any trouble with the lower mounting maybe you could contact the supplier & buy just the eyelets to fit to your shocks?

 

tell me about those handelbars, they look like some type of clip-ons

 

They are clip-on handlebars. They came with just a straight tube but I didn't care for the stance I rode in with them as low as they were, needed just a little more height to take my upper weight off of my hands. So I made the bars pictured above with the double 90 degree angles in them. Raised the height about 2 inches, just enough, but still keeps that really low profile look. The bars are made of 7/8 tube with a really thick wall. I also got the bars where I wanted them and tapped right through the clip and through the bars and put a bolt through it so that the bars can't twist no matter how much force ends up getting put on them. Also blocked the ends of the bars and put a 1/4 20 female thread on them for easy mounting of bar ends mirrors. Mirrors used to be on top of the bars and were absolutely useless no matter how you adjusted them. They work perfectly now and they look a lot better I think.

 

Bike looks great! How do you like the battery? I'm looking at a similar one for my bobber.

 

Battery is great. A little pricey but it is surprisingly small, only weighs 2.5 pounds and is more powerful than the stock one that was in it. There is no issue with the bike keeping it charged.

Ballistic Performance EVO2 8 Cell

 

It wasn't freezing cold out today so I got out to the garage to get a couple more pictures.

Here is one of the plug, they all look the same as this one.


And here is the seat

 

Looks so good man!

Also, HUGE +1 to the RP banner hanging in one of the pics!

 

Speaking of which, what's that under the RP banner? If it's half as nice as the XJ, then I'll want to see pictures of that, too!

 

The bike needs new front brake lines. Check the date codes on those original rubber lines.

Oh, and those plugs look nice. I'd say you were real close on mixture.

 

Thanks guys.

Yea, I probably should replace brake lines even though they look like they are in great condition and are plenty 'supple' and flexible. They are the originals from '81.

BaldWonder, the car is a Lotus 7 clone I built, I call it the "RX". It's powered by a 13B Wankel engine from a 2005 RX8.

Build photos here if interested:
http://daeds.com/Locost/photolog.php
Still haven't got finished photos up though for some reason even though it's been done for 3 years now. I did take this picture while I was out taking pictures of those plugs though. It's dusty and dirty as hell from sitting in the garage for months now.

 

Very nice! I bet that's a lot of fun.

 

Read this in regard to those brake lines: http://xjbikes.com/Forums/viewtopic/t=41400.html "Looks" ain't everything.

 

Is that the stock cluster and headlight for that year? My '82 xj750 Seca ha the square headlight and much more "80's" cluster, I have a cluster off an old '79 650 that I wouldn't mind swapping the stock one out for(as well as another headlight). I was wondering if you had done something similar or if '81 was just the last year they came with that style.

 

USA-market 750 Secas all came with the rectangular headlight(s) and "Atari" instrument cluster.