185S Blown Head Gasket

[Flyingw]

Hey guys,

I recently rebuilt an 81 185S including the motor. The motor was in great shape but somebody at some point put a Wiesco high compression piston in it. The cylinder was still round so I ran a hone through it and put it together. I used a run of the mill gasket set for assembly. I sent it home and they have ridden it. This weekend at the Rampage it started blowing cylinder compression out the head gasket on the right side but not every stroke???? It is intermittent when it is reved but it doesn't do it at idle. Strange indeed.

My question is...... Whats it worth?? Just kidding.

Is there a different head gasket I should have used with the high compression piston?

[oscarmayer]

Stop using junk gaskets and how did you torque down the head? If you did not properly torque it down the it will blow any HG. Use oem gaskets when possible. At lease for the HG. Cosmetic is the #2 on my list when I need a good one and oem is not available.

Check timing and valve lash. Those can all have an effect. Was the piston peeped prior to install? Sharp valve relief edges or dome edges can cause detonation. I would pull the piston and take a cartridge sand roll and take all those sharp edges. Small file could work followed by Emory paper to smooth. Run Emory across the entire top to take off matching marks and polishing.

Good luck. Of done right hi comp will last w/o issues for years. I have a 200x with 5 years and tons of hours on it with a 12:1 wiseco and ran perfect.


Sent from my iPhone using Tapatalk

[shortline10]

If you can find a copper head gasket that would be best and if it's a wiseco 12:1 piston it's a must but if it's their 10.25:1
An oem or generic should hold up fine also take note of the bore size most gaskets are for 65mm stock bores and a 66mm over bore might be to small .

[Flyingw]

Yes Oscar, the head was torqued. I didn't install the piston originally but it was in beautiful shape. The reason for my post is I read some posts suggesting a different gasket is required. I checked Weisco's web site and the only note I saw for the ATC was on the ATC 200 engines, 92 octane is required to avoid detonation. I haven't pulled the motor apart yet confirming the blown head gasket but 'm pretty sure that is the problem. I'll get back with you guys when I get it apart.

[oscarmayer]

I believe the Honda xr125 is the same but in a metal material and much better. Try one of those instead.


Sent from my iPhone using Tapatalk

[tri again]

I want to know the intermittent part of the story.
Detonation of oddball timing changes could change fire time.
Wishful thinking is spastic compression release?

This is an over the phone (customer) diagnosis?

Hope it's easy for you.

I too have a hi comp 200 and simply don't ride it.
Very hard on ropes and shoulders but roll starts ok.

[Flyingw]

I was there with it. I fired it up and it ran normally. When I hit the throttle it would puff out the right side but not every time. I agree its strange so I am curious when I do get it apart.

[Mr. Clean]

I think the issue is you have too much random stuff on the bench with that motor. That is NOT like you at all, you need to get better organized. Thanks.

[jb2wheels]

Jim, did you polish the impact guns?

[Flyingw]

Oh come on.... I'm not that bad.... I think.

[oscarmayer]

Honestly in my own experiences, the stock studs can wear out from use and age. You may have an issue of worn studs and they can no longer hold at stock settings. Look at maybe adding 5 to the stock Honda torque spec and see if that helps. Get the XR head gasket from Honda and that should work. That is what I run. That and cometic only.


Sent from my iPhone using Tapatalk

[yaegerb]

X2 on metal or copper head gaskets.

[Flyingw]

Copy that Mike. I'll get one on order this evening. We still on for this weekend? Disregard what I said about it being hard to start. Open the throttle just a tad and it busts right off. I took it to the ride this past weekend and it ran like a champ.

[Flyingw]

Is there a specific year gasket I should be looking for?

[tri again]

New bolts please.
We've had a epidemic of bvroken bolts from fatigure.
Ai await anxiously for the answer.

ssss NOT the comression release?

(i still need a new keyboard but no sympathy)

[Flyingw]

Say what????

[tri again]

Say what????
Sorry Jim.
Funky keyboard, frozen fingers still outside but lemmie try my main concers.

If bolts are loose, get new ones. we've had a few break with less than 18 ft lbs due to fatigue.

RANdom compression spitting "out the3 side of the head"...any chance it's an errant,
intermittent compreswsion release release type issue3?

Again.
I connot handle this keyboard. for this I apologize.

[Flyingw]

Oh ok, I understand now. Everything tightened down ok but I will add 5lbs to the cylinder head bolts on reassebly. Compression release is used to start it and all it does is open the exh valve but its disengaged when the cam rotates so not that. From what I saw, the gasket was allowing pressure to escape. Small puffs and no oil either. Either the gasket is just junk or an unevenness of the head.

[atc007]

Another vote for cometic being great gaskets. But on this one,,I Love Hondas updated head gaskets. Zero problems so far.But, they certainly aren't being pushed like the poor 200X's used to on a track. They are all I use. Threw one together Saturday for a local boy w his junk kit from the old days. O ring for the stud... Brought back memories lol. If it's blown on the right side,I would have guessed some oil seepage in the mix? Must be towards the front stud... Throw a OE one in and forget it,,after verifying everything in there is flat of course. Which I'm sure you already did once .

[Keith Salyer]

Yes, Jim blasted the impacts first, then polished them with 3 different grits and followed it up with Mothers and a diaper :)

[Flyingw]

Being one to admit my own shortfalls, I found the four head nuts were not torqued. The rocker cover bolts were but not the head nuts. They were loose enough to let the compression pressure to push past the gasket. I loosed everything up and torqued down. No more puffing. I remember I was pretty tired that night so I chalk it up to sleep depravation and being a trailprotrailprotrailprotrailprotrailprotrailprotr ailpro........ On to the next thing.

[jb2wheels]

Love an easy & cheap fix!

[Keith Salyer]

I like it when a plan comes together.. Way to go Jim

[tri again]

You're my hero.
Maybe I can tap into your source of luck?
Everything I touch lately breaks.
..and thanks for the reminder to get my torque wrench back.