Some cylinder head questions (with pics)

[mideastrider]

I too have a crf250 its interesting to see the condition of another’s engine. Just curious, are those the original valves that came in the bike?

 

[whenfoxforks-ruled]

Joe did one oem valve job, no seat cuts, yes? If you can get fuel in above ground, good. Anything below ground, not much difference, as long as its at least premium grade. Vintage Bob

 

[_JOE_]

Joe did one oem valve job, no seat cuts, yes? If you can get fuel in above ground, good. Anything below ground, not much difference, as long as its at least premium grade. Vintage Bob

No Bob, all original parts. I have extra OE intake parts but didn't install them. I thought they were going to crap out sooner cuase they tightened up so I bought the valves while I have a few bucks. Now that I look at everything I should have bought the exhaust parts too. I want to do the Kibblewhites but I feel sorta giulty about spending the money when I should be saving for bikes for the kids.

 

[_JOE_]

And the VP is in a 55gal drum.

 

[Rich Rohrich]

Rich, would running VP car fuel be better than pump gas?

VP has about 60 fuels in their catalog. Care to be more specific?

 

[_JOE_]

Wish I could. I can't recall. I'll ask next time I see him.

 

[_JOE_]

Does a new OE cylinder head come machined and ready for valve train?

 

[Pete Payne]

Rich, what is the "scag" in pump gas ?
I really like VP C-12.
Ol' Steve 125 is hooked on VP MR-9 right now . A little too pricie for me .

 

[_JOE_]

Does a new OE cylinder head come machined and ready for valve train?

Anyone?

 

[Rich Rohrich]

Yes, a new OEM head comes ready to run. I always like to check that the seats are concentric and true them if they aren't, but you should be fine just building a new head straight out of the box.

 

[Rich Rohrich]

Rich, what is the "scag" in pump gas ?
I really like VP C-12.
Ol' Steve 125 is hooked on VP MR-9 right now . A little too pricie for me .

Pete - Pump fuel has a bunch of high distillation temp components (upwards of 400f) that never vaporize and lead to the exhaust deposits that destroy the exhaust valves. Premium pump can be even worse in this regard because some of the heavier hydrocarbons that are used to boost the octane can have fairly high distillation temps.

Automotive engines turn so slow and have such long hot intake tracts that it's not a problem. But in the super short and relatively cool intakes in the current crop of MX engines, anything with a distillation temp above about 260f is unlikely to vaporize once the engine sees the far side of about 7000 rpm.


Here's an example of a good oxygenated unleaded race fuel and Illinois pump gas that sort of shows it in graphic form.

 

[_JOE_]

Thanks for the explanation on the fuel Rich. :cool:

From the looks of things I can get a new head for about the same price as a good valve seat machining after shipping and stuff.

 

[whenfoxforks-ruled]

I would jet with the blue fuel Rich, nice and stable. Them deposits get hammered into the seat, rings and seals, everywhere! All horsepower robbers. Curious statement about the crappy premium pump fuels, my favorite BP even had to go and add in some invigorate, I just know its not good! And nitrogen, what?, they believe the engine IS alive? Joe, probably another good move, nothing like a spare head laying around. Vintage Bob

 

[_JOE_]

It looks like I'll be doing the factory head and Kibbles after Christmas. I guess I'll have to take a ride down to the KTM dealer for some VP, no more sacrificing pricey cylinder heads to save a few bucks a year on fuel. :bang: For the 10 gallons of fuel I burn a season the extra cost will be well worth it. :cool:

I guess it's time pull the chassis down and grease her up. Hopefully we stay busy at work this winter so I can the boingers serviced too. :nod:

 

[whenfoxforks-ruled]

Hopefully we stay busy at work this winter so I can the boingers serviced too. :nod:

Be careful what you wish for, I have seen some forks get real pricey to service. Vintage Bob

 

[_JOE_]

I sure hope there's no suprises, though I don't have them serviced often enough so I guess it'll be my fault if there is. They work great and I don't beat the suspension at all, so hopefully seals/bushings/oil will be all they need.

 

[whenfoxforks-ruled]

Clunking is about 300 dollars. I am sure your fluid is black and thick, and about it. Change often, with the stupid timed drainage? Vintage Bob

 

[_JOE_]

Lol, I get the occasional seeping seal. Nothing a liitle cleaning hasn't stopped yet. I'm sure the oil is ugly. I wish I felt comfortable enough(had the right tools) to change the oil and seals myself.

 

[RM_guy]

... I wish I felt comfortable enough(had the right tools) to change the oil and seals myself.

Christmas is coming up, ask Santa for some tools :)

 

[_JOE_]

Christmas is coming up, ask Santa for some tools :)

It'll be a stretch for the elves to get my valves done in time, I'm not gonna push my luck. ;)

 

[whenfoxforks-ruled]

Changing fork fluid has to be the easiest maintenance to perform, but the shock you need to refill the nitrogen. Good suspension fluid is a bit pricey, compared to motor oil? The seals, be ware of the cheaper seals! If the seals keep getting contaminated, maybe you just need new wipers/dust seals? Vintage Bob

 

[_JOE_]

I think it would be silly to replace the dust seals without doing the fluid seals.

I did a fliuid change in my RM, it wasn't too bad but the suspension still sucked when I was done no matter how many adjustments were made. The shock was a b!tch, the forks were pretty simple. I'm in need of an oil level guage, cap wrench, seal drivers, and a few other tools before I'll crack into the CRF. Anyone got any used ones from a past bike they wanna part with? The Zook was old and crappy(molested) to start with. This one started out 100%, I want to stay as close to that as I can afford to keep it......

 

[whenfoxforks-ruled]

You do not measure the fluid on changes. Only on total rebuilds. The oem has a sweet time table, and how much to put back in it, got a stop watch? How much do you weigh in gear? Vintage Bob

 

[Pete Payne]

Thanks Rich !!!!!!

 

[_JOE_]

You do not measure the fluid on changes. Only on total rebuilds. The oem has a sweet time table, and how much to put back in it, got a stop watch? How much do you weigh in gear? Vintage Bob

I'm around 175-190lbs in gear depending on what type of riding and what time of year... ;) For some strange reason I'm always heavier in the spring? :whoa: