'82 Seca 750 Refresh Project: Now Scooby's Bike

Turn the carbtune upside down and use it that way

 

unplug the tci not the coils.... and if possible use a car battery when doing compression test


hows the voltage output of the charging system?

 

I'm not sure I follow you on this one.

I did the compression test.

No car battery, but what I did was I checked each cylinder with a full state of the motorcycle battery. I use the Battery Tender Jr which is great for bringing the battery back up to full.
Each cylinder checked one at a time with approx. 25 min between each for the tender to refresh the battery.

Engine cold. TCI disconnected. All plugs out. Admittedly it is a Harbor Freight compression tool, but the results were:
#1. 120 (120+ but not 125)
#2. 125
#3. 130
#4. 130

I believe Low Spec is 128

I can check if you give me some direction on that.

 

Just watched the video , okay here is observation when I use the Morgan tune the column should be about 1 to 2 inches on all 4 looks like yours are at bottom , I would try turning synch screws in till mercury increases in height till you can get them to equal an even height.

 

if the carbtune is trusted. the only thing that could affect vacuum across all four is the yics port

 

in this link it will tell you out put voltages of your charging system alsi test at higher rpm it should go no higher than 14.8 volts. just want to make sure you have enough out put to keep the TCI firing.
The Ultimate Relay, Switch, Sensor, and Diodes Guide

XJ650 and XJ750 air-cooled engines:
Minimum: 128 psi
Standard: 156 psi
Maximum: 171 psi
Max. variance between lowest and highest: 14 psi < this spec is the important one

a) make sure the engine is warm (at operating temperature).
b) remove all spark plugs, and then stick the plugs back into their caps and make sure the plugs are grounded to the cylinder head (or even better, disconnect your TCI unit).
c) remove the airbox filter lid and the air filter.
e) open the throttle FULLY and keep it open during testing.

 

Hello friends. I want to thank all of you for your comments and suggestions. Work has taken most of my free time over the last month and a half or so. While I have not sorted my problem out yet, I did have some time to devote to the project over the last two days.

I decided to pull the carbs again. When I pulled the set out, I found that slide #2 was stuck in the down position. I mean REALLY STUCK! I couldn't free it up with the tip of my finger. A flat head screwdriver did the trick... so I decided to pull the tops and bottoms off (did not separate the set) as well as slides, needles, jets, mixture screws, etc. give the bores and slides a buffing with a small soft wheel and put everything back together.

Bench sync is done again and wet set looks good.

Question that comes to mind is this...

Would the engine start and idle (all be it terribly) with a slide stuck in the down position? If this is the case, it would make sense that the exhaust for #2 get hot, signaling (to me) a firing plug... but obviously once running, #2 would not be "pulling it's weight" at throttle thereby leaving the other cylinders have to do more than their fair share in a less than harmonious situation. Then of course I'm over enriching things with the choke lever... ultimately making things worse... Black sooty plugs anyone???

I've run out of time to get the carbs back on the bike to see what the results are... Harumph....

Will update again...

 

the bike runs off of the pilot jet until you get to 2k to 3k rpm thats when the main jets start to kick in.
so the bike will start with slide stuck.

 

This feels like good news. I wish I had the time to get out there and reinstall the carbs. I hear them calling me!

 

Inlet rubber leak? on 1 or more carbs?
( or the dreaded carb butterfly rod seal leak(s)?

I'd love to know if you can get it running OFF choke, what it looks like after a high speed run (old fashioned hi speed plug chop)

 

I'd be concerned about a torn diaphragm. If it tore while the slide was up, the slide would fall quickly and possibly get stuck. Worth looking into.

 

I can confirm that all diaphragms are good... held each up to the light and everything...

Given the time to think things over, I’ve decided that I was over zealous (obsessed?) with lubrication and anti seize...

As I said, diaphragms are in great shape, but perhaps I should not have massaged them with silicone grease. During this last disassembly, I wiped off excess grease that I now realize just didn’t need to be there... maybe between the unnecessary anti seize (as discovered earlier in this thread) and the grease, I inadvertently created more problems...

Guess I’ll see when I get the carbs back in... looking forward to the weekend already...

 

Well, hopefully you'll get her running soon.....be interesting to see a high speed 'plug chop'.....and, also find out what the 'backfiring' through the carbs might be??

Where in Suffolk County are you located??, I'm probably close by, if you need a second opinion/set of ears/eyes, lol........though I'm nowhere near as good a (XJ) mechanic as I used to be, lol !!

 

i put silicone grease on the diaphragms but just a wee little dab

 

Ok, so essentially, no change.

Benched sync done again. Carbs back on the bike. Another brand new set of plugs put in just in case. Choke on, turn the key, hit the button and she started right up. Raced up to 6-7k so I rolled the idle knob back to a reasonable level (lets say 3-4k) while the choke was still on and she warmed up. I let it go for a few minutes and after some time went by, I began gradually removing choke.

Sync gauge showing 1, 2 & 4 relatively the same height with #3 very low.

However, as she continues to warm and I attempt to back the choke all the way off over time and adjust the idle knob to keep the idle at a reasonable level, she goes into a rhythmic up and down cycle of the RPMs... and then it happens... The Sync gauge tubes begin to pop from the intake nipples!

Whoa!

I also saw a blue flame come from the #2 nipple after the gauge tube popped off.

New plugs just as black as the last set.

 

you want your idle to be 1050 rpm (spec) 1100 rpm
when choke sends rpm up back off choke. see where you can drop it to and still run no less than 1100 rpm the choke makes motor run at higher than idle rpm.

carb 3 adjustment is the idle knob use the knob to bring up #3 vac then tune down the other carbs to 3.

 

Are your valves in spec/closing properly, I wonder....?
(also, valve timing good?)

 

not to say he has more than 1 issue going on. the leak down test is used for valve leaks.
psi going up with oil is oil sealing the gap in rings to cylinder walls.

 

I missed the bit where he'd already tested the valves/rings to bore....

I suppose that only leaves the carbs then, if the valves are in spec, and the rings are sealing......

I had poor WARM starting,( but not cold) and spitting back ( massively) thought the carbs when my 900R ate its valve guides/inlets.......I was convinced it was the carbs, turned out the valves/guides were sinking into the head.....not a known XJ problem,I know !

 

Today she started as usual... Took a few tries, but she gets there.... displaying the usual popping and rough stuff...

It's clear to me that #4 is not firing. Or at least not consistently or strong enough for that matter. I hooked up one of those spark indicator things and it appears to flash as if the coil is doing it's job. On previous attempts (other days) all 4 were getting hot... though, once I checked it initially, I never checked later on for risk of burn... I just assumed once she got hot, she'd stay there.

Throughout the trial today (several minutes), I can leave my hand on the exhaust. If I did that on the others, I'd definitely leave my skin behind.

Question #1. Can one side of a coil go bad?

Question #2. I'm getting a reading of 4.5 -ish on the coil thin wire resistance check... The book says it should be 2.5 + or - Isn't this high? Honestly, The cap to cap test does not seem to give me any display at all. I'm doing something wrong I think...

Question #3. Can I swap the 1 & 4 leads to the plugs to see if the cylinders swap the "no fire" condition?


Also noteworthy... I clipped the #4 lead back, cleaned the screw shaft inside and replaced the cap. I cleaned the carbon from the #4 plug and put it back in. Bowl levels look good (I thought maybe I was back to a starvation problem but clearly it is not) and after this last attempt, the plug came back out squeaky clean, but wet with fuel.

 

get a temp gun 15$ aim and test save the burnt fingers

the plug wire can go bad and the connection where the wire goes into coil.

primary wires (thin ones) meter should be set to 200 ohms
secondary wires (sparkplug wires) should be tested at 20k setting with out the caps on the wires.
go to next highest with caps installed

you can swap leads to see if problem follows wire and cap. you can also swap plug into known firing cylinder to test plug

regap plug?

 

you have to get the sync right first. try turning the idle knob till you get some kind of reading on #3, then make the rest match 3.

that says #3 was shut off, the idle was too low

 

Ahhh, This makes sense... however now I need to get #4 firing first...

 

maybe that would work but the better way is to get the sync closer first. even if you need to disconnect the tci to keep it from starting and running away, and just get it closer with the starter.
with the sync that far off #4 may not fire when 123 do and vise versa.
there is another way, pull the carbs and get a good bench sync. didn't want to hear that, did ya

 

I’m not opposed. It would be the 6th time I’ve had them off the bike. The last time, (only a few days ago) I decided to pull them again and re bench them. At bench sync, the vacuum looks like that. #3 is low and 1,2&4 are high and relatively similar. As it stands now, I’ve not touched the sync screws, only the idle screw...

I just assumed that I NEEDED all firing to do the vacuum sync.

 

don't get me wrong here, it will need to run around 1k to 1.7k to get the sync close and tweek the mixture screws. it seems, as it is now it runs on 1+2 and maybe 4 hits now and then. that could be the

that's#4 coming and going .
you need to turn the idle up (that opens #3) now get on the 1-2 to 3-4 screw and while the starter cranks try to bring 1-2 down closer to 3
stop, take a brake, let the starter rest
get on the 3 to 4 screw, hit the starter and get #4 down closer.
somewhere in all this, it's going to start at a reasonable rpm, then you can tweek and tune till your happy

 

Seems like you have a strong suspicion that it isn't a coil/electrical issue.

My "to attempt" list is growing.

I'll give it another go this week end. That's the next chance I'll get to go out there and try...

 

better to rule out things before spending money that you do not have to.

I do agree with Polock that your carbs are way out of sync or at least thats the place to look.
swapping plugs and wires is a good teat yu also maybe able to swap ignition coils around too

 

the plug caps on these coils are connected to the same wire, it goes up the plug wire, around and around many many times inside the coil and goes out the other plug wire.
so if something happens to that wire, both plugs quit. same with the 12v side, it's all or nothing

 

OK. Small success. I set everything back up and gave it another try. Given the idea that I'd try to sync without worrying about #4 NOT firing, I set out on my task.

Got her running and I kept the RPMs up with choke on while I tackled the sync. As I said before, 1, 2 & 4 read significantly higher than 3... 1 & 2 were nearly the same with 4 being even higher than 1 & 2.

I didn’t pay attention to how smooth it was running, my goal was to bring the 4 carbs to the same level. Over time I was able to back the choke completely off. I got real close with the sync… low and behold, when I reached down to feel #4, it was screaming hot! All 4 were firing.

However, there was still a fair amount of popping. So much popping in fact that my sync tubes for 1 & 2 would not stay on. I think that once warmed up, the sync gauge tubes get so soft that they can’t hold on to the intakes anymore under the popping pressure... Also worthy to note is that 3 & 4 do not have this issue.

I decided at that point the sync was close enough... I couldn't keep the gauge attached to the engine anymore anyway. I put the caps back on the intakes (the caps won’t blow off while popping!) and I played with the enrichment screws a bit (1/4 turn either way as @Polock suggested earlier in this thread). While it was hard to discern a rise or fall in the idle while turning the screws, I was able to affect the popping.

The popping became minimal and the cyclical, deranged up and down of the idle disappeared.

I’m happy to say that I put her back together and was able to ride around the neighborhood a bit. It is no where near where it needs to be, but I feel like I got her far enough at this point to not feel totally defeated by it.

At throttle blip, the idle takes too long to come down, but of course more tuning is necessary. I’ll tinker as time permits. I will register and insure her in the spring as she will be making the trip back to the carb clinic in June... Next to one of her sisters on the trailer of course. I’ve no doubt she needs only a few minutes with the master (@hogfiddles) to dial it in.

There's still a long road ahead. She still needs a lot of love but there's a ton of life hiding in there. I know it.

 

Any more updates?

 

No updates yet. When the weather breaks a bit, I'll pull her back out. I have other XJ's so I'm able to ride all year, but wrenching in the cold is a bit annoying for me.

I'm convinced it's a mixture issue at this point. Lean? Rich? Who knows. She's definitely on the "to do" list in the spring and as planned, she's getting one of the spots on the trailer for Carb Clinic #13. I'm hoping all will be sorted out by the end of that day.

In the meantime, there's little things to deal with. New throttle and clutch cables (or at least better/correct ones) and a few other details will be tended to. Every once in a while there's a grinding at the push of the starter button. Starter? Starter clutch? Not sure on that one either. It seems to be consistent with a hot engine. It's not every time and I've not found it to happen when cold.

Will update more here when I know more.

Cheers. It's Friday!

 

OK boys. The parts came back from the machine shop. No more broken bolts and screws. That means it's cleaning time to get ready for rebuild. As ya'll saw from my last post. My gaskets were baked on. So, I've been removing them with some aircraft remover. Which is safe for aluminum I assume since well.. it comes in aluminum case. But I noticed it was stripping a layer off some parts. I'm not sure what it is. I need to repaint the frame as well since it's a bit rusty. Aircraft remover works quite well. Do ya'll do the same?

 

good stuff with the correct gloves

 

Is it good to use on crankcase and what not? I'm not sure if that's chrome paint being stripped off or not. Or something else

 

works on the motor only chrome would be the nuts on the head as far as motor goes . silver paint and clear coat black paint. .

 

Plese, please, please keep all posts about fixing your bike in one thread. The history of what you do really helps us all keep track of what's been done, and how to give you the best advice when new issues come up.
Let me know which thread you prefer as your main, and I can merge them.

 

Ya of course. I didn't think I needed much help but as I got deeper and deeper into the engine, more issues popped up. You can merge it with Nuch's thread.
https://www.xjbikes.com/forums/threads/82-seca-750-refresh-project.125467/page-5

It was his bike before I bought it.

 

What you are stripping off in the pic is the very tough, original, silver engine paint. Most of the XJs had silver-painted upper crankcases, heads, etc; if they weren't painted black. I use Aircraft Remover, very carefully, to remove the original finish from parts I want to polish or repaint. I say very carefully because, as you can see, it works almost too well.

 

It looks like they also paint inside the crankcase? Is there any point to doing that or should I just strip the old paint on everything and only paint the outside

 

No clue, but yes they do. If I pull the "oil pump cover" ("YICS" labeled cover) from the right side of my 550, which is just a blank naked area except for the crankshaft oil seal, it is obvious the upper crankcase is painted and the lower not. And that's an "internal "area. I suspect it's not actually paint paint, but some sort of high-heat coating that they may have dipped the parts in, hence it being inside and out.

I'd leave it alone on the inner areas you can't see.

 

It used to be that any casting that might be even a little porous got a coating of Gyptol (red), and later on high-temp paint was used (mostly on aluminum). Don't strip any of what's inside of the cases just to be on the safe side.


Thread merge complete. Redirect expires in a day (I goofed), so bookmark accordingly.

 

So I'm stripping the paint from the frame cause it was rusting up. Figured I should recoat it. Been taking the paint off with aircraft remover. Which is a long and messy process. Issue now is getting the gel in those hard to reach spots and scrubbing off the paint. So I'm thinking of sandblasting the rest off? Is that a no go? Maybe the frame can't handle it. Maybe sodablast? How do ya'll remove the old paint from your frames?

 

Well it can handle it, and the results will give you a great base to prime and paint.
So here's a pic of the FZX after a professional media blast:


Taped over the VIN sticker and the two blue plugs are to keep any blasting material from entering the coolant tube in the frame (you won't have to worry about that).
Cost was $125. plus tax of course.
American Dry Stripping did the job for me. Their in Milford, CT but you should be able to find someone reputable near you.

Tony

 

Hey guys.

I took apart the brake calipers. The top part of the caliper has its grommets melted away. I don't know how that happened. I guess just from age and the calipers soaking up all the dirt from the road. Any fix for this? Is it a super important component of the caliper?

 

Those weren't grommets. Those were the caliper pin boots, and yes they are necessary. I did a write-up a few years back on the 550 caliper, and your bike uses the same type: https://xjbikes.com/forums/threads/splitting-the-calipers-on-a-xj550.40994/

 

xj4ever sells them. they protect the pin that goes through them

 

Caliper needs to float and the pin needs to stay clean and greased to be able to float, so yes need to get the part.

 

The Yamaha "holding block caliper" is a rather unique bit of engineering. The piece those boots belong to is the 'holding block' that bolts to the fork leg. The caliper essentially hangs from a large pin that goes through those boots and the block. The caliper needs to be able to slide laterally in relation to the block to compensate for pad wear. Those metal plates are to protect the sliding surfaces from each other, do not lose or discard those. There is another, rectangular-headed pin that holds the pads in; the "sliding pin" is the connection between the caliper and the block. If experience is any guide, you will need to replace the sliding pin when rebuilding the caliper. I've usually had to pound them out due to being rusty/corroded, and they generally don't slide very well any more.

 

Roger that. I'm trying to replace almost everything that looks a bit beaten. Costly but why half ass a rebuild