'82 XJ750 Maxim Build Summary + Links to Tech threads

Quick updates: Got some new cables, fashioned up a rear fender/light/plate mount instead of the mount/light down at the axle. I also crudely polished the sides of the tank while leaving a strip of rust along the top, and finally found an exhaust collector to use from an 81 Seca. I imagine that with some slip on mufflers this will make the bike run even better than it does now, thought I'll need to tune the carbs again.

I sort of need to do that anyway, as over the past two weeks the bike has developed somewhat of a hanging idle when I pull the clutch in, or rev it over 2,500 at a standstill. I don't know if it could be that I need to adjust the valves again also, but I'm going to do that when I pull the carbs to clean the slides, jets, etc. These were zestfully cleaned last winter and the bike didn't sit for more than 3/4 days at a time since it was warm enough to ride.

I'm a little stumped about that hanging idle though, since it hasn't done it until very recently.

Anyway, here's some new pictures:

This is the new rear light/fender setup:



Plenty Bright:


Here's the bike at the Distinguished Gentlemans Ride in Pittsburgh:


And here's the dapper fellow that rides it:



This winter I'm going to have everything painted/powdered/cleaned and I'll probably take the top end off and do maintenance on all of those goodies. I'll also do new brakes/lines/suspension.

I'm happy to say that I was able to get version 1.0 of my CB running and rideable as of two weeks ago, but it needs tuned badly, so it's sitting for now. I also have lots of cleaning up and modifying to do, so I have a feeling that I won't get to take it on any long rides until next year.

 

Looks awesome man! I'm in the 7th layer of tuning hell right now on my newest project & I'm fighting a hanging idle issue almost exactly like what you described. Far as I can tell from researching it's caused by a lean condition and the most likely culprits are a vacuum leak around the intake manifolds or a clogged pilot circuit (but could also be wrong sized jets, leaking throttle shaft seals, or....). I ruled out the vacuum leak on mine so it's time to tear the carbs down again. Ugghgghgh.. I just want to ride it. Then sell it.

 

Interesting, I'll have to check that out. To test the vacuum leak around the intake manifolds, I would simply spray unlit propane around the area no?

Would that catch my throttle shaft seals as well?*

I did replace these before spring, but never hurts to double check.

Thanks everyone.

 

Yeah that's the test that I've read about too. I tried it & didn't notice any increase in RPMs but I wasn't convinced so I pulled the boots and put them back on with new gaskets and some copper RTV just to make sure. It didn't help. Not sure if the propane test works with the throttle shaft seals but I would think so. If that's where air is getting in the it would be sucking in the propane too. I didn't replace my throttle shaft seals because of time, money, and pure unadulturated laziness. Plus I've always been a little scared of breaking the rack apart but I'm sure (just like anything else I've learned on these bikes) it's probably not as bad as it sounds. I got away with it on my first bike and never had a problem but it might be coming back to bite me on this one.

I'll keep you posted if/when I get mine figured out.

 

Have the carbs been synched?

 

Yeah mine have been synched. It was tough because it wanted to either barely run or it would hang at a higher rpm and sometimes race up. Need to double check my jet sizes too I think.

 

Ted, I broke the rack on my carbs with no prior mechanical experience (Well, nothing to that magnitude, not even close). Check my post on it, I think it should really help with anyone weary of stripping them down. TONS of photos and diagrams: http://www.xjbikes.com/forums/threads/first-time-taking-apart-carburetors-lots-of-pics.48063/

My carbs were synced using the two bottle method and did great all summer, but since I've randomly developed a hanging idle AND due to the fact that I need to sync the CB carbs, I think it's time to buy a four gauge setup and a carbtune. I'll have to double check, but I'm pretty certain the CB and XJ have different plug threads which is unfortunate.

I have this other idea (which I hope someone can weigh in on, because I just thought of it) that my clutch may have been adjusted improperly. Two weeks ago, before the hanging really started I decided to do an emergency "Guidectomy" for the hell of it, just to see if I had any plastic guide chain pieces floating around in the engine. I did, however, open the wrong side of the bike where the throwout rod is (DOH) and so I had to put it back together and re-adjust.

I'm wondering if I was too sloppy with the adjustment, and now when I pull the lever, if the clutch isnt engaging fully, leaving me with that idle. Does that make sense?

Regardless, I'm excited to get the exhaust collector in place so that I can finally get this thing to run like a top, and backpressure is definitely the key.

So in the next few weeks I will certainly be pretty active on here again, because there is much tuning to do before winter!

 

if the clutch has too much free play it bangs going into gear, creeps forward at red lights and engauges as soon as you start to let it out. not enough free play and it might slip.
the two bottle sync tool is more accurate than the individual tubes because you can see the accumulated difference over time

 

Good info. It seems that the best method might be for me to use the two bottle sync paired with the colortune.

 

I love the color on that Honda. I'm sure you've already told us, but what year/size is it? SOHC, so 70s, right? Always wanted CB Honda four, but hoped the XJ would suffice. Your posts are making me think "Not so much". Damn. Put it back on the Xmas list.

 

Same! It's a 73 CB750, and the color is called Candy Buccus Olive. Though I will be powdering the frame and other various bits, I'm not touching the original paint. For being 42 years old it's in great shape despite it's "character" involving various scratches and whatnot, but I like the "patina." I have yet to clay, buff/wax which ill do this winter to make it pop a little more; It's fantastic in the sun, and since I wanted to do brown leather for the seats (and grips, they'll be wrapped in matching brooks) the color matches very well. The seat I have now was something I made/upholstered just in case I got to ride it before winter. I'll be having it done by the same guy who did my XJ seat.

Really can't speak for the performance/fun factor, however. I've only taken it around the block!

I digress from the point of this post, however. The seca exhaust collector came in and I threw it on a moment ago, then took it for a 5 minute ride.

HANDS. DOWN. The best thing I've done for the bike. It idles better, runs better, and it may have actually cured that hanging idle, but I won't really know until I ride it long enough to have it at normal operating temperature. I'm thinking that crosspipe is really the key, considering that Ted was able to have his old maxim run well with pods and shorty exhausts, but not with an aftermarket 4-2 that didn't have the crosspipe.

I used his suggested jetting setup by using two small washer shims on the needle, and bumping up to 124 mains.

I also think that meat under the frame makes the bike look way better than when the headers were open. Function AND Form!




I believe will be chopping it up a little to run two shorty cones directly under the frame as opposed to them jutting out the side, but that's a winter project. I guess I'm just highly advocating using the stock collector and running custom pipe behind it. Therefore, please excuse the sloppy wrap job on the pipes, no sense in fixing it now. Lastly, these side profile shots realllly make me want to do a wheel conversion this winter.

 

I don't know what "Candy Buccus Olive" means, but it sounds gross! If my kid got some for Halloween, he'd be pissed! Looks great though.

 

It's said that Candy Buccus Olive is what comes out of someone who eats too much Candy on Halloween.

I look forward to much more XJ fun this winter.

 

Does anyone here have any experience with these oil temperature gauges that replace your oil filler cap on the case? They look nice.

http://www.mandp.co.uk/index.php/de...ge-xjr1300-fz750-xj550-xj650-xj750-xj900.html

 

You're right but that's about it. What can you do about the oil temperature?

 

Look at it.

 

Eh, take a peek here and there; I'm curious to see the temp at which I'm running anyway. Wouldn't that help me determine the engine overheating if I'm sitting in traffic?

 

Your engine will not overheat while sitting in traffic. The finning is designed to allow the engine to idle at a standstill without overheating.

 

Then why am I instructed to place a large fast fan in front of the bike when syncing the carbs (since the bike is sitting dormant idling)? Not being condescending or anything, just curious to hear your thoughts.

 

The idea is that you will likely be working inside of a garage where there is no significant airflow. The other issue is that the YICS blocking tool can get stuck inside of the YICS passage once the engine gets hot enough to melt the rubber seals. The fan buys you working time (not using the tool buys you even more working time).

For some perspective: I did 30 minutes of freeway riding last summer in KC. 30 minutes at an average speed of 1.2 MPH (sitting for several minutes was welcome as working the clutch in that sort of traffic really sucks). I had not a single sign of overheating (typicaly resulting in sluggish throttle response as the pistons begin to soft-seize and the valves begin to burn, or pinging as the combustion chamber temperatures rise).

Now then, if you're waiting on the longest train ever....just shut the engine off and wait; it'll save gas.