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Ural Spark Plug Compression Leak Repair



I had noticed a hissing sound coming form the area of the left (non-sidecar) side of my 1998 Ural Tourist 650cc engine.  Upon closer inspection, it became apparent that I had a compression leak.  I could hear a hissing from the spark plug and could feel the leak at idle and while manually cranking the engine with the kick starter with the ignition off.  That side spark plug had always been a "bear" to install as the fist thread was cross threaded.  So I guess it was time for a repair.


After posting the problem to the Russian Iron Motorcycle Club Forums message board, several people suggested an spark plug insert kit.  Gene at Holopaw Corvette, the closest Ural dealer, suggested a Helicoil Sav-A-Thread kit.  I picked up Helicoil kit no. 5334-14 from my local Advance/Discount Auto Parts store for about $26.00.


Items you will need for this project:
- Helicoil Kit (P/N 5334-14). 14mm x 1/2" reach
- Tube of High Temperature "Red" RTV silicone sealant
- New head gasket (I don't know the part number, got it from Gene)
- Metric hand wrenches and socket wrenches
- Hammer
- Miscellaneous hand tools
- Torque Wrench (yes I finally broke down and bought one)
- Exhaust clamp spanner wrench from Ural tool kit
- Rubber Mallet (to gently persuade sticky parts)
- WD-40 (I love that stuff, I put it on my breakfast cereal, no not really)
- Lots of rags (I like the red "shop towels" you get at the auto parts store)
- Oil Drain pan
- Beverages!  (I suggest non-alcoholic until you get done at least)

Note: You can click on each of the picture on this page to view them in a larger size, use your browser's "Back" button to return to this page.

Here's some of the items from the list:


Helicoil Sav-A-Thread Kit

High Temp RTV Silicone

New Head Gasket

Spanner from Ural tool kits - use the one on the left to remove the exaust pipe clamp.


Warning - This operation requires removing the cylinder head.  If someone tells you "don't worry about it" they are full of s**t.  Way too many metal shavings will get into the cylinder if you try this without removing the head!!!

First place an oil pan under the cylinder valve cover (trust me on this, I learned it the hard way once).  Use a wrench and remove the valve cover retaining nut.  About an ounce or two of oil will drain from the valve cover.   Hence the need for the pan...

Take note of the valve rockers and pushrods.  I cleaned them real good with a rag and marked them "intake" and "exhaust" with a Sharpie marker.  With the ignition off, slowly crank the kick starter by hand until the cylinder is in about "top dead center" position.  At this point both valves will be closed and you should be able to twirl or spin the pushrods.  This removes the pressure on the pushrods and make it easier to disassemble.


Next, remove the carburetor.  Loosen the clamps on the rubber hoses on both sides of the carb, the rubber hose going to the air box and the compensating fitting connecting the carb to the head.  You do not need to remove the compensating fitting.

Next, remove the "J" exhaust pipe.  First, mark where the edge of the pipe meets the head, that way you'll have an idea of how far it goes back in when you reassemble it.  I just took a flat blade screwdriver and gently scratched on the pipe along the edge of the head.  But then again, my J-pipes are blue, rusty and look like crap.  If yours are shiny and you don't want to scratch them, use a Sharpie marker Loosen the clamp holding the pipe to the frame, and use the Ural spanner wrench to loosen the clamp that holds the "J" pipe to the muffler.  At first, neither of these clamps wanted to budge, but after a few squirts of WD-40 (I love that stuff) and about 10 minutes time for it to settle, they popped loose easily.  While the WD-40 set in, that's a good time to go get another beverage...  Once the clamps are off, use a rubber mallet to tap the exhaust pipe loose from the head with a few gentle taps in the middle of the J.


Here's some more pictures:


Valve cover removed

Close up view of pushrods, rockers, and valves.

mark the exhast pipe

carb removed

clamp holding pipe to frame and clamp holding J pipe to muffler

clamp holding J pipe to muffler

exhaust pipe loosened

exhaust pipe removed



OK, now that the carburetor and exhaust pipe are removed, you need to remove the engine guard.  Trust me, I tried to remove the head without removing the engine guard first.  If your leak is on the sidecar side, "sucks to be you".  I don't know if there's enough clearance to pull the head without removing the sidecar.  Fortunately my leak was on the easy (non-sidecar) side)

Next you'll want to remove the rockers and pushrods.  Again, I suggest marking the rockers "intake" and "exhaust" so that you put them back right.  I used a plastic tray in my garage lined with paper towels and laid everything out exactly how I removed them. Also note which pushrod is which and remember which en goes in the tube and which end the rocker rides on.  Again, laying these out in a tray helps a lot!!!.


The head and rockers are held in place by the same four nuts (if memory serves 12mm).  Remove the four nuts and place them in the tray.   Then gently remove the rockers and the bushings that sit between the rockers and the head.  Place them in the tray.  I even noted which were the top and bottom bushings, although they appear to be the same size.  The pushrods will then fall out.  Catch them and put it in the tray noting which side went in the motor.   Pay attention to remember which is the intake pushrod and which is the exhaust.  With my tray it was easy to keep them all straight.  Once you have these parts out, put the tray aside.  Get another beverage...


Here's some more pictures:


Notice the four nust holding the rockers and head on the cylinder

My "tray" with all of the rockers, pushrods, bushings and nuts. I marked arrows showing which way the pushrods went ba

nuts, pushrods and rockers removed

Doh! - I need to remove the engine guard to get the head off!

engine guard removed

a head in the hand is worth two in the bush

Egads Luther, its the headless cylinder!



Once I had the head removed, I could really see how bad the treads were in the spark plug hole:



OK, now the fun part...

Read the instructions carefully on the Helicoil Sav-A-Thread kit.  Yes, I know that "real men don't need instructions", but do it anyway!!!   The kit contains a special tool with two different diameter taps with a built-in reamer between the different taps (pretty freakin' clever if you ask me).  It also contains an expander tool, and three different length inserts.  The middle size (1/2") is the one you'll need.


First, lube the tap and the spark plug hole.  I didn't have any thread cutting oil handy, so I just used a little 20W50 motor oil for lube.  Start the tap slowly by hand into the spark plug hole.  The smaller diameter tap on the end of the tool is the same diameter as the plug threads.  Make sure the tap goes in straight.  This was a challenge as the first thread in my spark plug hole was cross threaded.  But with a little work it was in straight.  Once you have it started, place the head on a flat surface and use a socket wrench with a long handled ratchet  and slowly turn the tap.  Use plenty of lube!  Once the smaller diameter tap goes through the threads, the reamer part of the tool will cut a larger hole using the existing threads to pull the tool through.  It gets a little harder to turn the ratchet, but go slow and use the lube.  Once the reamer is through the larger diameter tap part of the tool starts cutting a larger thread.  Again go slow and use plenty the lube.  I found that a small paintbrush was an excellent help to keep lubing the tool.   Once the larger diameter tap goes all the way through, blow off some of the chips and reverse the ratchet and slowly back the tool out of the hole.   Wow there were a lot of chips.  Blow all of the chips out of the hole and head (if you have an air compressor).  I don't have an air compressor so a brush and some spray carb cleaner did the job real well.  You made it this far? Great, reward yourself with another beverage!!!


Here's some more pictures:


tap started by hand

close up of tap started

starting to come through (lots of chips)

tapping done - look at all the chips

view of helicoil tapping tool

get all of these chips out

these would have been in the cylinder if I didn't remove the head first - UGH!

view of threads once chips removed


Now it's time to put the insert in.  OK, following the directions on the Helicoil kit, grab that tube of high temperature RTV silicone, and apply some lightly to the threads of the insert.  take a spark plug and spray the threads of the spark plug with some WD-40.  Screw the insert on to the spark plug making sure that the slotted threads will be at the top of the spark plug hole (look at the Sav-A-Thread directions), as the hole is recessed, we will need to use the spark plug to screw in the insert to the freshly cut threads.  Carefully screw the insert into the new hole and tighten snugly with a ratchet.  Once tightened, reverse the ratchet and back out the spark plug (the insert should stay in the head).   Check to make sure the to of the insert is flush with the top of the spark plug hole.  If so get the expander tool from the Sav-A-Thread kit and place it flush in the top of the insert and smack it gently a few times with a hammer (but not too hard), I found the peen end of a ball-peen hammer worked well.  This locks the insert into place.  Goth this step done? Great!  Get another beverage!


Here's some more pictures:


Insert in. Yes it's supposed to look like this as the hole is larger and the head is domed

top view

after insert seated properly with expansion tool



Now that the spark plug insert is installed, it's time to re-install the head.  use a screwdriver to pry off the old metal head gasket and place a new one on the cylinder.  Then slide the head back on.  Go get that tray with all of the rockers, pushrods, bushings and nuts.  Put them all back in the same way you took them out.  Start with the bushings then the pushrods, then the rockers and then the nuts.  Do one side first and then the other.  Just hand tighten them for now.  When you put the pushrod back through the tube, you'll feel it slid into place.  I'm not sure exactly what it rides on, but you'll feel it go into place.

Once you have everything hand tight, grab the torque wrench.  On my 650, the manual says the head nuts should be torqued between 22 and 24 ft-lbs.  I split the difference and went with 23 ft-lbs.  Check your manual as the torque specs vary by engine and year.


Be sure to tighten the nuts in a "star pattern"  or "cross pattern "for even tightness.    I started "snugging" the nuts with the top exhaust and then the bottom intake, then the bottom exhaust, then the top intake.  Give each a turn and then go to the next until they are all torques properly.


Once the head is torqued properly, you'll need to adjust the valves.  I'm not going to go into great detail on how to adjust the valves.   For what it's worth, some folks like the "twirl method" others use a .004" gap.  I personally set the valves with a .002" feeler gauge.  I put the feeler gauge between the tappet and the valve and snug it just so it holds the feeler gauge set and tighten the locknut.

Once the valves are adjusted, you're almost done!  Install the valve cover gasket and valve cover.  Re-Install the engine guard.  Slide the exhaust J pipe back through the clamp that holds it to the frame, slip on the clamp that holds the J pipe to the muffler, and slide the J pip into the muffler.  Grab that tube of high temperature RTV silicone.  Smear a little on the end of the J pipe that goes into the head.   Line up the J pipe with the exhaust port on the head and use a rubber mallet to tap the J-Pipe back into the head to the line that you marked on the pipe earlier.  Tighten the pipe frame clamp and the pipe to muffler clamp.  Re-install the carb and tighten the clamps on the compensating fittings and hose to the air box.  Clean, check the gap and reinstall the spark plug and you are done!

Once I was done, I manually cranked the motor with the kick starter and no more hissing from the spark plug hole.  The Sav-A-Thread directions say wait until the RTV silicone is set before running the motor and the instructions on the RTV tube say it takes 12-24 hours for it to cure, so I won't be able to ride it until tomorrow.


Job well done, now have a good beverage!!!  I like the ones with fermented barley and hops myself...

Here's the last of the pictures:


torquing the nuts

23 ft-lbs. (check your manual)

nuts torqued and valves adjusted

install valve cover


high temp RTV on J-pipe

J-Pipe installed

reinstall spark plug

reinstall carb and spark plug wire




John Grocke


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