That would be a water pump seal letting coolant into the engine.

 

Thanks guys, I was never really aware of oiling the threads but the reasoning does makes sense. I'm going to talk to Eric, get everything I need, and be a little more careful with this install. The fact that Jed hasn't had a failure and pushes the amount of N20 he does gives me some hope[img]i/expressions/face-icon-small-smile.gif[/img]

 

<div class="FTQUOTE"><begin quote>Originally posted by: 650VIPER

I have never had a head gasket failure, but I have fixed some that have. Most of the time, I have seen the bolt on the chain side loose, not the stays. And even with a good cometic, they will still leak.
</end quote></div>

I got around to taking the head off this weekend. Before pulling it I checked all the bolts first. All of the main stud bolts were still snug, but the waterjacket bolt you descibe that is closest to the timing chain was definately under torqued. My guess is it was somewhere around 15ft/lbs or even less. After pulling the head it was obvious from looking at the discoloration in the gasket this is the area that was leaking into the cooling system. I guess you can add another one to the list of failures you have seen. I wonder what it is about that particular bolt that makes it more prone to failure than the other bolts?????

 

Well, sorry to hear that, but its an easy fix. I do not know what causes that bolt to loosen. I figured on the ones I seen it was tightened before the stays, and then lost its torque from them.......but I am not positive. Just make sure to fully torque your stays before you start on the outer head bolts. Double check them all before you close her up, and ride it like its stolen.......well heck, I know you do that anyhow.

 

Do not torque 8mm to 24
Do not torque 10mm head bolts to 44

If you overtorqued head, that may be the reason you blew a gasket.

The factory studs are good, but the nuts if overtorqued, stretch.
That is why, even if torqued properly, I would change nuts after 2 uses.

Bombardier DS 650 Torque Data

ENGINE
Engine Support M8 26 N.m (19-20 lbf.ft)
M10 64 N.m (47 lbf.ft) Note- Cylinder head bolts not to be torqued more than
37-38 lbf/ft.
M14 135 N.m (100 lbf.ft)
Spark Plug 22 N.m (16 lbf.ft)
Magneto Nut 180 N.m (133 lbf.ft)
Starter 10 N.m (89 lbf.in)
Starter Red (+) Cable 4 N.m (35 lbf.in)
COOLING
Radiator Mount Screw / Nut 10 N.m (89 lbf.in)
Radiator Protector 2.5 N.m (22 lbf.in)
Temperature Sender 35 N.m (26 lbf.ft)
Water Pump Cover 10 N.m (89 lbf.in)
Fan Mount Screw / Nut 3 N.m (27 lbf.in)
Oil pressure Switch 15 N.m (133 lbf.in)
EXHAUST
Exhaust Nut 11 N.m (97 lbf.in)
Heat Shield Screws 10 N.m (89 lbf.in)
FUEL
Carburetor Mounting Clamp 0.6 N.m (5.4 lbf.in)

DRIVE TRAIN
Front Wheel Hub Nut 135 N.m (100 lbf.ft) (MINIMUM)
Rear Wheel Hub Nut 235 N.m (173 lbf.ft) (MINIMUM)
WHEEL
Wheel Nuts 52.5 N.m (39 lbf.ft)

STEERING / CONTROL
Upper / Lower A-Arm Lock Nut 60 N.m (48 lbf.ft)
Tie Rod Ends 75 N.m (55 lbf.ft)
Steering Arm (castellated nut) 75 N.m (55 lbf.ft)
Steering Column Support Screws 24 N.m (17 lbf.ft)
Handlebar Screws 24 N.m (17 lbf.ft)
Flanged Bearing Bolts 10 N.m (89 lbf.in)
SUSPENSION
Shock Absorber Bolt Front 48 N.m (35 lbf.ft)
Rear 85 N.m (63 lbf.ft)
Front Upper Swing Arm 67 N.m (49 lbf.ft)
Front Lower Swing Arm 67 N.m (49 lbf.ft)
Rear Swing Arm LH First Nut 100 N.m (74 lbf.ft), Unscrew Nut a Quarter Turn
Rear Swing Arm LH Nut 100 N.m (74 lbf.ft)
BRAKE
Caliper Brake Screws 24 N.m (17 lbf.ft)
Brake Disk Screws 34 N.m (25 lbf.ft)
BODY / FRAME
Front Bumper 24 N.m (17 lbf.ft)
Rear Extension Frame 48 N.m (35 lbf.ft)
Footrest 10 N.m (89 lbf.in)
Skid Plate 4 N.m (35 lbf.in)

 

Jed,
Yeah I am pretty sure when I put the head on hte last time the stays were the last bolts I torqued down. I figured since those are only 89in/lbs they would not have any affect on the other head bolts but I guess I was wrong. That was probably why it lost its torque. I have all new bolts/nuts from Eric this time and will be a little more cautios with this install.

 

Jed,
Yeah I am pretty sure when I put the head on hte last time the stays were the last bolts I torqued down. I figured since those are only 89in/lbs they would not have any affect on the other head bolts but I guess I was wrong. That was probably why it lost its torque. I have all new bolts/nuts from Eric this time and will be a little more cautios with this install.

 

OMR,
thanks for all the TQ specs. I will definately keep those for reference. I confirmed with Eric (HPR) that the factory torque specs are too much. He also recommends only going 37ft/lbs on the studs and 20ft/lbs on waterjacket bolts.

 

how hard is it to change the head gasket?

 

Its not all that difficult if you can turn a wrench and have some patience. It does take a while. I just got mine put back together last weekend after replacing the head gasket. Do yourself a favor and pick up a shop manual if you don't already have one. Also make sure you have a good quality torque wrench when you go to put the head back on.