Starting an 850 MkIII after, um, 10 years

For a black boyer box better to use a non resistor plug cap and HT leads, for red or blue then use only one of a resistor plug, cap or HT leads.

Plugs come out easier when the head is hot, less likely for the thread to strip from corrosion.
 
Have I missed the bit where we talked about thoroughly cleaning out the carbs and passages and jets?

Sounds like a blocked carb passage to me.
 
Fast Eddie said:
Have I missed the bit where we talked about thoroughly cleaning out the carbs and passages and jets?

Sounds like a blocked carb passage to me.
Click to expand...
I removed and cleaned the main jets, and poked a soft wire in all the other passages and jets, and verified that spray cleaner went through where it should. When I initially disassembled the carbs, everything looked factory new inside except the bottom of the bowl.

I've cleaned old Keihin and Hitachi carbs several times before and these were pretty pristine looking by comparison. The bike was fully restored in the early 2000s and then ridden for not more than a few hundred miles.
 
kommando said:
The pilot jet is a 17 thou hole, you clean it with a 16 thou #78 drill. Nothing else works 100%.


See page 5 for pilot bush position.
Click to expand...
I just measured the wire I used with dial calipers, it's 0.016" or 0.017" depending on which caliper you believe. However, even though I read that article a while back, I missed the pilot bush. Ah well. Pull 'em again and we'll get it done!
 
jh850es said:
I just measured the wire I used with dial calipers, it's 0.016" or 0.017"
Click to expand...
The danger with using wire is that you push the debris back into the pilot feed system, it then can come forward again when you use fuel and reblocks the pilot jet. Hence why the drill is recommended over the wire, the flutes of the drill fill with the debris and this is removed when the drill is pulled out and so cannot be reintroduced.

Use the drill, as @LA.B. says the pilot bush is accessible from behind the pilot jet screw. To go deep enough to fully clean the pilot bush the drill will need to be extended, easiest way is to epoxy it into an aerosol can tube used on WD40.

Starting an 850 MkIII after, um, 10 years
 
I checked both plug wires with a timing strobe, both appear to be sparking.

I ran the wire into the pilot bushing. I'm skeptical that this particular bushing is .016". It didn't feel clogged, and in fact felt like it has to be bigger than the .017" wire. I didn't measure the exact depth but it was about the length of the adjuster screw + 1/4" or so. I'll look closer when I have the carb off.

I also put a Carbtune vacuum balancer on and adjusted the stops. I ran out of time before I could try it upside down. I know this isn't the factory balance method, I was mainly interested in the vacuum reading in case there was a huge air leak. There does not appear to be a leak.

The sum total effect of this work today was that it runs on one cylinder still, exactly like before. Next step: pull the carbs, verify everything.

The good news is that is started on the second kick after sitting for a week. I don't get how it can start so easily and run so badly but here we are.
 
Have you checked compression? If you don't have a test guage, you can feel whether they're broadly equal with your thumb over the plug hole.
 
Mart UK said:
Have you checked compression? If you don't have a test guage, you can feel whether they're broadly equal with your thumb over the plug hole.
Click to expand...
Also , I've had to replace both bowls . The screw in tabs were warped from over tightening , air was entering from the bowl gaskets .
 
Just reamed the pilot with a .016" wire. Seems like it might in fact have been blocked, based on the airflow I was getting before and after.

It turns out I did have my dad's compression tester and it registered about 123 psi when I kicked it over a few times.

Still running on one cylinder.

Went back, reamed the left pilot and gapped the right plug to .025".

Running on two cylinders now!

Went around the block a few times. Running like a dream. Idle needs to be reset after last week's fumbling around, but basically it's all good.
 
Pulled the front master cylinder. The piston is rusty enough that it might need replacement. The sleeve is not obviously damaged so far. I'm going to put the piston on the lathe and see if the surfaces clean up enough to be usable.
 
A cleaned up but pitted piston that was still sized correctly will work as its the seal that does the work and the piston just makes sure its centralised. But if its gone rusty once it will again so if you can get a replacement then replace.
 
I ran a nylon pick around the sleeve and it felt fine. The piston cleaned up OK where it counts. Everything's back together and the lever feels firm and doesn't sink during a long squeeze. Road test to come.

The guys on youtube really need to get some of these picks. I got the seals off and on with zero tears (in the rubber or from my eyes), quite easily.
 
Last edited:
Everything worked great riding around the block a few times this afternoon. Rear master cylinder still pending but *fingers crossed* it should go as easily.

You'll have to follow me over to some to-be-determined Triumph forum when I kick off the 1983 TSX recommissioning project in a few weeks.

Thanks for all the excellent advice!
 
jh850es said:
Everything worked great riding around the block a few times this afternoon. Rear master cylinder still pending but *fingers crossed* it should go as easily.

You'll have to follow me over to some to-be-determined Triumph forum when I kick off the 1983 TSX recommissioning project in a few weeks.

Thanks for all the excellent advice!
Click to expand...
There's a triumph section on here
A lot of us also have an interest in triumphs
 

Similar threads

J
  • Locked
Starting an 850 after 8 years
2
Replies
25
Views
3,159
Schwany
Schwany
P
  • Locked
Commando 850 - 10 years storage
Replies
4
Views
942
paclx
P
mprchrgr68
  • Locked
Sage advice needed for an 850 MK3 ES rebuild
Replies
10
Views
2,050
L.A.B.
L.A.B.
R
  • Locked
What to expect first start in 10 years.
2 3
Replies
52
Views
3,757
DogT
DogT
B
  • Locked
Starting an 850
Replies
8
Views
1,226
Cookie
C
Back
Top