Milling the head question.

[rigger]

Now I have another bug to try and work out of my R project.

I had a little coolant leak on the head gasket before and I thought I had two studs that were messed up and that is what was causing the leak.

I checked the head and it measured out to be ok. It was in spec. But it must still have a problem because it is still weeping around the head gasket.

What do you guys think of the possibility of I just have a bad head gasket?

Now if I take my head and cylinder to my local machine shop and they end up milling the head and the top of the cylinder, where can I get a thicker head gasket to make back up the difference?

Or does anyone have any other ideas or things that I should try?

Wish I had the money to say ^*&$ it and just go get a new 310 top end for it. That would be cool !

[IcutMetl]

Well; to my knowledge, you have at least two options that I know of.

Option 1:
Have your head cut to flatten it out; it will probably only take a few thousandths. Use stock head gasket, check static compression. As long as you're under 180-185psi or so...good to go on premium. Anything over; throw a mix of race fuel in with it. I took apart my gasket and only run a .010" thin portion all together (without cutting the head) and got 195+/-psi and run a 50/50 mix- runs awesome. Probably the cheapest route; any given machine shop can set the head up and flatten it out.

Option 2:
Send your head to a shop experienced with these motors(there are many). Let them know what your situation is and what you'd like them to do. Have them cut the head, and re-chamber the dome. When you put the stock thick gasket back on; whambo...stock compression. Or...whatever you choose. Probably the better, but slightly more expensive way.

Either way; go to the auto parts store and get a can of Permatex Spray Copper; when you put your head back on, spray both sides of the gasket and let the stuff tack up. This helps to fill in small voids, etc, as the head is torqued down.


Good luck!

[deathman53]

I would take off the cylinder and head. Bring them to a machine shop and have them flattened. Its basically where he/she rubs them on a perfectly flat block, usually with grooves or a piece of emery cloth is put on it. The cylinder might need to be decked slightly. Then get a thick trx250r head gasket, spray it with cooper-coat before applying(wait until tacky). Then put everything back together, base nuts 35 ft/lb and head nuts 20 ft/lb, some will argue over lubing the threads, they say it changes torque value. I always do, I'm not sure it makes it more torque or less. You shouldn't have any more headgasket problems.

I had a cool-head some years ago with this problem, I rubbed it on that machinists block, new gasket(sprayed) and the problem was done. I still have that head, I removed it, as I wanted to use pump gas. I'm gonna use it on my next motor build and hopefully for the woods bike I want to build.

[rigger]

Well I was at about 195 on compression already so I am guessing this head as already been milled before. That is why I am thinking I would need a thicker head gasket if it got milled again. Checked it today before I cranked her up and it was down to 185

I was not to concerned about this because I know I had a lot of oil and gas in the crank and figured that may have bumped up the compresion a tad since the fluids dont compress. But when I got back from putting down the street and back and saw the coolant weeping, I know I must have a head problem.

Or I guess I could have a crappy head gasket too. Guess I am going to take the top end off and take it to a shop to at least have it checked out and see what the deal is. Then take it from there.

If I can't fix it with just some machine work and gaskets, she is going to have to sit for now. I can't afford to get any big money parts right now.

Thanks for your thoughts guys.

[IcutMetl]

Deathman is right. What he's talking about is called a lapping plate. It is a dead-on flat plate of hardened steel, with intersecting grooves milled into it; the machinist will spread clover compound (lapping compound- like greasy, abrasive toothpaste) onto the plate, put some die-bluing on the bottom of your head/top of cylinder, and swirl it around on the plate until all the bluing is worn off evenly. If done right- at that point, it should be as flat as you'd need it to be. He could also do the same thing with some light oil or kerosene on light emery cloth placed on top of a granite inspection plate. It's actually pretty easy to do.

Orrrrr....if you have something like a really clean, flat, ground, non-damaged surface(like a newer table saw???), you could essentially do the same thing. I did it to my head before I put it back on just to clean the face up some. Clean the mating surface off with acetone or carb cleaner, then instead of bluing- use a permanent marker on the entire surface. Use light emery and plenty of solvent, light oil, WD-40, etc to lubricate and repeat that general process- keeping very light pressure until you see all the marker disappear. This won't remove much material; if it takes more than a few tries- have it machined. Use your best judgement if you're comfortable trying this or not; it's definitely a "cheap & dirty" way, but it works just fine.

[rigger]

That is what I am going to try and do next. I don't mind doing the work, I just did not think of that before. Don't know why.

I have been told before that I can reuse the head gasket that I have now since it has only been on for a short while and has only gotten hot now twice. I know it would be better to get a new one but just wondering how many of you guys have tried to reuse the head gasket?

Maybe my local Honda shop will have one in stock but knowing them, they won't. The parts guy there did not even know what a 250R was the last time I called just checking to see if they had something in stock.

[2muchquad]

put some emery cloth or i have taped 600 grit sandpaper to a piece of glass(its perfectly flat) and a bit of oil and hold the head on the abrasive and do figure 8s repeatedly until you have a fresh clean surface,i have done that many times over the years.Now if you really want to take some material off use some valve grinding compound,but since your just truing your sealing surface that wont be necessary;)

[86 Quad R]

these guys are right. you can do this yourself. i have a 2' square laminated plywood that i use for this. i take a large sheet of(wet type) fine grit aluminum oxide and attach it with the 3m spray adhesive. works great. after a couple minutes of lapping it'll be evident where the low spots are. good luck with it. :cool:

[croat1]

figure 8's is the key just like 2much quad stated

[Honda 250r 001]

Originally posted by 2muchquad
put some emery cloth or i have taped 600 grit sandpaper to a piece of glass(its perfectly flat) and a bit of oil and hold the head on the abrasive and do figure 8s repeatedly until you have a fresh clean surface,i have done that many times over the years.Now if you really want to take some material off use some valve grinding compound,but since your just truing your sealing surface that wont be necessary;)

I too have done this before but getting the head studs out can be a *****, i have head great results though.