Should I continue my 84 FJ600 project or is it not worth it?

Hello all, first time poster here. I'm a 28 year old in the Denver area and just started my motorcycle journey in October 2022 but I need some advice on if you think I should continue working on my 84 FJ600 or if you think I should focus my effort and money on a bike that is more complete/running.

This is my first bike but I felt confident in my ability to work on it/diagnosis issues as I grew up working on cars and have a Mechanical Engineering degree. I do brakes, suspension, oil, and other general maintenance on my own car and have done some work on the engine of a 68 Pontiac Tempest. I bought the FJ600 back in October off Craigslist knowing that it does not crank/start easily but the seller did get it running when he showed it to me and it sounded good and I knew that it needed a few things fixed (needed a new battery, rear caliper rebuild, carb synch, etc). Cost was only $1100.

Things I've done/fixed on the bike so far:
Rear brake caliper completely rebuilt and rear master cylinder was replaced.
Carbs were taken apart and cleaned, bench synced, and fuel level set.
Intake boots patched/sealed with gasket maker.
New intake gaskets installed.
New spark plugs.
LED headlights, taillights, and turn signals.
Tank cleaned and new petcock installed.
New fuel lines, filter, and vacuum hoses were installed.

Issues that I've discovered/have come up since I've started to get into the engine:
(Everything is cylinders 1->4, left to right)
Plug conditions (signs of old plugs and new plugs installed):
Black/sooty, black/sooty, good color but wet, good color

Low compression
Dry: 59, 106, 27, 12
Wet: 115, 136, 34, 24

Too tight valve clearances (Specs: Intake 0.11 to 0.15, Exhaust 0.16 to 0.2)
Intake: <0.04, 0.09, <0.04, <0.04
Exhaust: 0.12, 0.16, 0.14, 0.13

Needs a new 1/4 (left) ignition coil. I accidentally pulled the 4th cyl plug wire out last night because I thought the plug wires were like a car and easily removable/replaceable. Since the wire was pretty easily pulled out by hand I suspect that some of the copper was already broken and this ignition coil would probably need to be replaced anyway.

Even with those issues (before breaking the plug wire) I had gotten the engine to crank and idle. Usually a little rough.

So my question is do you think it is worth it to continue to take the engine apart to further diagnose the issues and fix them (cylinder condition, piston rings, valve shims) or do you think I should save the money required to fix the issues and put it toward a bike that I know would be running or just require some basic maintenance and have replacement parts more readily available (from a dealer or even brand new). Thanks for any and all advice/comments.

 

I'd do the valve clearances first, which might be contributing to loss of compression.
A lot of bikes get laid up when they get reluctant to start and the PO doesn't know enough or can't afford shop time.
There's also a very good chance the compressions will come back up once it's been running for a few miles (that might be anywhere between 10 and a 1000 miles), it's not uncommon on a bike that's been sitting for years, where the ring packs have got stuck.
The dodgy intake air boots will need replaced sooner or later, but they might be good enough to get it running right - or at least not contribute to its bad running.
As far as coils go, I use MT-08 coils from Hondas - fitted to many 4 and 6 cylinder Hondas for years - they've got replaceable HT leads, unlike the standard ones.

Simply taking the above steps won't cost much and will give a much clearer idea of what's wrong, if anything.

 

100% what Dave said. Compression could be valve clearances and you will likely see the numbers come up once it's been running.

Even us bike guys have bikes get laid up, my Max has been sitting since 2017 and I bought a Seca 650 from the original owner in 2019 that I haven't started yet.

 

Appreciate the advice. I might just be having a moment of being antsy and just wanting to start riding. I think I'll go ahead and replace the valve shims to correct the clearance and replace the bad ignition coil then reassess after that. I know the intake boots are dodgy but they work for now (sprayed carb cleaner while idling and didnt see any rpm changes) and I'll get replacements if I can get the compression up and bike running normally.

Do you have any additional information on those MT-08 coils? Link to some on sale or specific honda model/models you got them from? Tried googling "MT-08 Honda ignition coil" with poor results.

 

A triple set from a GW 1500, leaves you one spare.
Notice the replaceable leads.
Ideally, you can replace the leads, but chances are those original leads are fine for a long time yet, and should reach plugs 1 and 4, and easily 2.3. Just remove the plug caps and fit NGK resistance caps.
https://www.ebay.com/itm/314329623418
They vary in price a lot, but can commonly be found for between $20-$30 for the set.
If you hunt also for CBR1000 coils, they also pop up. You only get two in a set of those, though.

 

Thanks. I found an oem ignition coil on ebay for like $25 and ordered that. Installed new valve shims last night and did a cold compression test which showed better but still low numbers. It's alot easier to start and idle is so much smoother now. It revs up well but hangs a bit at 2750/3000 rpm but I'm pretty sure that's because I have an air leak with the #3 cylinder intake boot. Will get it up to temp to get more realistic compression numbers and hunt down/seal that air leak this weekend.

 

I run Honda CB750 coils you can still purchase these new and fit in stock location, Cycle Recycle part 2 has these coils for 40$ each and they have the wires and caps as well.

 

That will be one sweet bike when you get it sorted. Old bikes can try your patience from time to time, but the end result has always been worth it to me.

 

@mosedocta it looks like you are still coming here, so I hope I can give you some incentive. I have an '85 FJ600 that took quite a bit of work to get back running again, but now that it is, I am really enjoying this bike. It is hard to believe it is now 38 years old because it still performs well!

One of the things that finally helped me get it running correctly was replacing the intake manifolds and shaft seals, even though I could not detect any leaks. I also changed the jetting a bit to account for E10 gas, but the only change that I think was critical was the pilot jet. Here is a link to the thread that I documented my journey:

https://www.xjbikes.com/forums/threads/fj600-jetting-dilemma.128374/

 

@Hollybrook

I really appreciate the advice and link to that thread, I'll be sure to go through it. I bet I'll have to do some rejetting eventually as well considering the bike came with 4-1 exhaust, pod filters and I don't know if the previous owner compensated for the Colorado elevation.

I actually got it out of the garage, down the street and back on its own power the other weekend so that was a good morale boost to keep putting work into it.