Jump to content

Reusing unused but compressed head gasket?

Recommended Posts

Kinda did something dumb during my rebuild on my XR400, forgot the o-ring on the cylinder base.

Only realized it was missing after I bolted the head on. 

So I took the head and the cylinder back apart, installed the o-ring. No problem. Base gasket seemed fine to reuse. 

The head gasket is the layered style, made of steel I assume. I reinstalled it but now i'm debating whether to order a new one since it is a one-time use crush-style.

I gave the head bolts 38 ft lbs instead of 33 to hopefully get a little more crush out of it.

Any thoughts? I've never had a problem when doing this before with a new gasket. But i'm getting more picky the more engines I work on.

If this was a water cooled bike i'd probably be replacing it right now. But air cooled? No coolant to dump into the cylinder? Am I just being overly paranoid?

Edited by mudguy

Share this post


Link to post
Share on other sites

I don't think your being overly paranoid. Just cautious. That's a good thing. At least you discovered the issue early.

Now my question.  Have you run the engine through a heat cycle or is it a virgin/cold assembly?

If it's a cold assembly I would give it a try w/the original gasket. You can always replace if it's faulty.

If it's been run, (heat cycled) I would definitely replace it.  Ride safe👍. G, in Vegas. 

ps, , don't use ANY sealant on the gasket.  Dry is good. Torque to spec.

Share this post


Link to post
Share on other sites
10 minutes ago, PaydayGabe said:

I don't think your being overly paranoid. Just cautious. That's a good thing. At least you discovered the issue early.

Now my question.  Have you run the engine through a heat cycle or is it a virgin/cold assembly?

If it's a cold assembly I would give it a try w/the original gasket. You can always replace if it's faulty.

If it's been run, (heat cycled) I would definitely replace it.  Ride safe👍. G, in Vegas. 

ps, , don't use ANY sealant on the gasket.  Dry is good. Torque to spec.

Has not been heat cycled, just bolted it up and then realized I forgot something.

I'm thinking it's either going to leak immediately or be fine for just as long as normal

If my metallurgy knowledge is right, if the studs are steel and the cylinder & head are aluminum, then it's going to get compressed a lot and set during the first heat cycle i think? Because aluminum expands almost twice as much as steel.

 

Share this post


Link to post
Share on other sites

head gasket is viton coated MLS. Can be reused. The purpose of the layers is to allow for thermal expansion with the aluminum. Torque to spec. 

Edited by redhurricane

Share this post


Link to post
Share on other sites

sounds ok but I would not run it with over torqued head :naughty:. you run the risk of ripping head studs once you heat it up. be careful torque specs are there for a reason.

  • Like 1

Share this post


Link to post
Share on other sites
6 hours ago, vicxr400 said:

sounds ok but I would not run it with over torqued head :naughty:. you run the risk of ripping head studs once you heat it up. be careful torque specs are there for a reason.

I'll tell you what, in the interest of science, i'll run this at 38 ft pounds and if it is too much i'll let you guys know.

  • Like 1

Share this post


Link to post
Share on other sites
On 7/28/2017 at 9:39 AM, mudguy said:

I'll tell you what, in the interest of science, i'll run this at 38 ft pounds and if it is too much i'll let you guys know.

Absolutely, do not overtorque unless you like buying a new cylinder.  Don't play engineer.  Honda already did that job very well.

Or it already leaked and you're making a futile attempt to fix something that cannot be fixed?

Share this post


Link to post
Share on other sites
1 hour ago, Baja Rambler said:

Absolutely, do not overtorque unless you like buying a new cylinder.  Don't play engineer.  Honda already did that job very well.

Or it already leaked and you're making a futile attempt to fix something that cannot be fixed?

No, it hasn't leaked, seems to be running quite well.

Im actually a bit concerned now because I guess I'm supposed to have torqued those studs wet and they were dry. So they might possibly be under torqued...

I think I will pull the cam out and give them an oil and retorque. 

Speaking of torque, this 426 is a monster. On pavement it wants to lift the front wheel at every intersection.

It might actually be a bit too much with the BSR42 carb.

Jetting is really rich right now, thinking about dropping 2 sizes on the main and pilot.

And maybe increasing the clearance on the exhaust valves slightly because the ADC is kicking in a bit too much for my liking.

Share this post


Link to post
Share on other sites
7 hours ago, mudguy said:

No, it hasn't leaked, seems to be running quite well.

Im actually a bit concerned now because I guess I'm supposed to have torqued those studs wet and they were dry. So they might possibly be under torqued...

I think I will pull the cam out and give them an oil and retorque. 

Speaking of torque, this 426 is a monster. On pavement it wants to lift the front wheel at every intersection.

It might actually be a bit too much with the BSR42 carb.

Jetting is really rich right now, thinking about dropping 2 sizes on the main and pilot.

And maybe increasing the clearance on the exhaust valves slightly because the ADC is kicking in a bit too much for my liking.

My 250 leaked from previous owner's monkey work.  I kept replacing gasket and each time, I eventually had oil running down cylinder from compression leak.  After third time, I checked torque before pulling it apart and it was below spec., replaced cylinder and fine ever since.  What a PITA that was. 

At thiis point, on yours', I think I would just run it rather than pull it apart again.  

On 250, sleeve drops out of cylinder in oven at +350F so I swapped sleeve out of freezer and clamped into a good used cylinder from oven saving my recent bore and piston.

Share this post


Link to post
Share on other sites

Bike has been running well so far.  Head temps are hugely lower with the 426 kit for some reason?

I have not seen a head temp over 180 so far. Previously I would routinely see mid 200s and i've seen as high as 280 coming off the highway all heat soaked and coming to a stop.

I wonder if blasting all the dirt off the cylinder and head improved the cooling.

I ended up one jet size lower on the main and one lower on the pilot.

I don't understand why a big bore with slightly higher compression would be running cooler. Perplexing. 

 

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×