Re-re-reviving my '81 Seca 750

There might even be one more 're' in there. I was active on these forums back in the aughts and early teens, but for dumb reasons I can't fully fathom, I unceremoniously put my 1981 XJ750RH Seca up at the end of 2011 with 37k miles on the clock.

I got carb kits and shaft seals from Chacal back in August of '11 and . . . just never got around to doing the rebuilds. I had my WR250R to ride. Then more kids came along. Then a move. And then in 2020, I pulled it out of storage, had absolutely zero brake pressure, lots of oil seepage on the lower part of the engine, and I got overwhelmed/discouraged.

But I'm back at it now. Here's what I know I need and I'm trying to figure out the order to do them in. I'd love to just order all the parts and hit it, but I need to budget over at least a couple months.

1) Rebuild carbs. The bike was running great in 2011, but I was getting gas in my oil while parked as the bowls seemed to drain in to cylinders. I'd cleaned them in the past, but never did a proper rebuild and shaft seals are original.

2) Rebuild master cylinder and replace (YIKES) original brake lines. Going stainless.

3) One oil change w/ Sea Foam and then fresh oil/filter after that.

4) Rebuild clutch. AFAIK, it's original. Was getting some slippage, IIRC, though that could have been down to contaminated oil. At any rate, I'm replacing the friction plates. I had it open tonight and the drive plates look good.

5) Tires, sadly, were pretty fresh in 2011 and have tons of meat, but of course are WAY out of date.

6) Battery is way past dead.

7) Replace final drive oil, basic checks of electrical, cables, etc.

One thing that concerns me before I do any/all of that work, (especially the clutch work/replacing that gasket) is the large amount of oil seepage at the lower front of the engine. When I was riding it regularly, I had some seepage around the valve cover gasket, despite always putting a fresh one on after valve adjustments, but never lower. I'll attach a pic for opinions.

Also, when I had the clutch pack out tonight, I noticed the inside of the clutch compartment looked really good EXCEPT the low spot. There seems to be a good bit of, I don't know, spalling? in that little well. The rest is smooth, as is the underside. Is that normal? Possibly from water in the oil freezing in the low spot? Is it a concern?

And finally one other question about the clutch plates. The couple videos I've seen of XJ clutches mention the drive plates having a tab which is supposed to be repacked in a certain pattern. I don't see anything like that on these plates. Is that not a 750 thing or are these not OEM? BTW, the friction plates are actually in better condition than I expected, but yes, I do plan to replace them anyway (as well as springs and bolts).

Also also, I know about rear brake delam. I put EBC shoes in there sometime in the last 5k miles. I will inspect before I get rolling again, but at least they're not the OGs.

Anyway, glad to be back around. Hope I hang in this time. Nice to see a lot of familiar faces and many new ones.

Please chime in with any guidance/warning/encouragement.

 

Yes, one suggestion - clean the fuel tank and petcock. Then, once the carbs are clean they will stay clean. 99% of issues on these old bikes on here is carb related.
More pictures please as you progress.

 

Good call. Petcock was rebuilt before the lay-up and tank was good last time I checked, but I'll add a once-over to my list before I splash new gas in there. Also, I do run an inline fuel filter which will be replaced.

I think my current plan is to get fresh oil in and try to spark her up with the carbs as-is just to get some oil circulating in there and see how that goes. With that benchmark set, I'll do carbs and order the brake rebuild parts. See how that goes, and hopefully by next billing cycle be ready for clutch parts and battery (I have a donor battery for now, just wrong form factor). I'll do my best to document.

 

Got fresh oil in tonight, a donor battery connected, and an aux gas tank with slim hopes of it actually firing. Almost sounded like it wanted to kick over at one point, but then I caught whiff of the float bowls leaking, so I pulled the plug and pulled the carbs. Rebuild will probably commence this weekend. Note to self, idle screw was about 13.5 quarter turns out before I messed with it. Didn't touch anything else yet.

I do have lower rebuild kits and shaft seals already, but think I'll be ordering more parts to do it right after all this time.

 

I hope to get a full weekend update written sometime today at work. ;-)

But right now I have a question about the front brake rotors. Does anybody know the original thickness? I know minimum is 4.5 mm, and I have 4.85 with very minimal run out at 37k miles. I'm just wondering how much mileage (ballpark) they've got left. I don't have any notations of prior thicknesses, which is a bit unlike me. I'll of course keep an eye on them going forward after a few thousand miles.

Thx

 

@chacal do you know the original thickness of the rotors on an XJ750rh?

 

Pretty sure stock is 5mm, although I do not know for a fact. The FSM should have the specifications.

 

Yes, 5mm is original thickness, so after 37K miles you're half-way to min. thickness........so maybe another 37K miles before getting out of spec. Stock brake rotors are made from an incredibly hard material. Using metallic or semi-metallic pads will increase friction, provide better stopping power, but will eat up rotors more quickly.

 

One item , your valve clearance and at same time replace the valve cover this should take care of your oil leak.

 

@Jetfixer Thanks for the tip. The seepage seems lower than the valve cover, but I AM going in there for a valve check while the carbs are off to dfox for detox (AKA The @hogfiddles Summer Camp for Wayward Carbs and Stuck Floats) - tracking says Out For Delivery! And a new valve cover gasket and pressure washer bolts are on order from Len as soon as I work out a small cash flow blockage. I can't give the case a good scrub/degrease at the house, so my plan is to work on mechanics now and cosmetics when I can ride her to a self car wash (yes, I know to be careful w/ high pressure) and get a better idea where the oil is from.

Also going to do a compression test before I get too far ahead of myself (getting a gauge tomorrow). A little worried about how long the jugs sat un-loved, but it did crank pretty easily a couple days ago (i.e. not seized, but hopefully nothing the other way, too).

I'm overdue on a big write-up, but it's percolating. If anyone wants to see recent tear-down pics (brakes and clutch mostly), I did upload a slew to ye olde Flickr: https://www.flickr.com/photos/oblivion/albums/72177720301209843

 

They have so much fun up there. They get to run around and play, swim in solvent, all kinds of fun carburetor activities. Mine came home so happy.

 

You PROBABLY meant Factory Service Manual, but I prefer to read it as Flying Spaghetti Monster. I hadn't seen a start-thickness in my Haynes manual. I have XJCDs around here somewhere, but thankfully Len piped in to concur with your 5mm, and that's good enough for me to ballpark my remaining wear.

 

LOL. I waste a LOT of my own time, but occasionally I realize it is worth something, especially with so much else to do on this bike. My time saved plus his expertise made it an easy decision. I'd already half-assed them once almost 20 years ago, so at over 40 years old, they deserve to be full-assed for once.

 

When you do valve clearance a metric feeler gauges are major requirement. I recently bought some from Northern hydraulics . I have several that supposedly had both SAE and metric...I call BS the set I just bought were like 9.00$

 

Yeah, I've done the check before, so I've got the holding tool and the gauges.

Cleared one hurdle today. Got a new plate for her. I was a little worried this might be a hassle, so thought it good to get it out of the way before dumping more cash in. The problem is that the original owner got the original title with the "shorty VIN," which I also did, both here in Illinois, in Wisconsin when I lived there a couple years, and then again coming back to Wisconsin. The first time I ever realized there was a longer VIN was when I changed insurance companies and they rejected the shorty VIN. So I'd found the sticker on the headstock and . . . part of it is rubbed off. I was able to reverse engineer the full VIN thanks to searching here for the code, but I worried getting it back in the system (I'd let the plate lapse in 2015) was going to raise some questions, might need a cop to clear it, and they might not be happy about the obscured sticker. BTW, mine was manufactured in February of '81 - just months before they started stamping the full VIN. But that's future me's problem. Like MIGHT be a problem if insurance ever gets involved, but . . .

 

And when you know what shins you need...... you know who runs the shim pool, cough cough

 

I've been meaning to confirm that rumor. Would make sense to drop a couple in the box on the return trip if needed. I'll let you know.

 

Compression was within a needle's width of 150 on all 4 cylinders. 2 dead on 150, one at 145, one around 152. Not bad after sitting 11 years.

Valve clearances are good on 7 of the 8 valves. Have to find my misplaced stash and see if I need any shims. Not a bad Saturday morning. Even had the 8 year old helping me out a bit.

There is a bit of grimy oil settled in the top. Will get what I can out of there. Hoping a run with seafoam once I get going cleans things up.

Will be dropping a big order on Chacal soon. . .

 

Today spent a little time with the gas tank. Petcock is good. No gas when there shouldn't be and gas with vacuum or prime. From what I can see inside, very minimal surface rust. I may hit it with a light treatment of Evapo-Rust anyway since I have it on hand. Thoughts? I used it last year to revive a scooter gas tank that sat full of water for at least a year. Did wonders.

Also picked up some new spark plugs yesterday. Old ones look good and don't have many miles on them, but why the hell not?

 

Spark plugs easily last 10k miles today, usually twice that, so I would at least keep the "old" ones for when the new ones are worn out.