CR250r VHM cylinder head setup

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2/1/2018 2:41 PM

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What is the best way to adjust squish/piston height? These are the specs that came with the VHM head. My engine is getting a complete over haul this winter and I want to make sure everything is done as perfect as could be. When I was younger I just enjoyed riding my bikes and mostly kept them stock. Now at 28 I have almost as much fun working on them and trying different mods. Advice from the pros would be great.
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2/1/2018 10:28 PM

Not a pro

If i'm right you get with vhm 3 different insert to choose and a fourth to make ur own.
A- higher compression for hardpack.
B- standard compression allrounder.
C- lower compression for the deep sand.

First of all what kinda tracks do u ride and what kinda power are u searching for. What kinda pipe are you riding with.

Example. I did ride with pro circuit and a base gasket of 1.2mm in sand. It gives no bottom power.
Now i ride with a 0.6 base gasket in sand.
Now i have a new handbuild pipe so now i'm gonna try to see how this works with the .6 gasket. If the power is enuff from the bottom. I can choose to get back to 49 sprocket of go to a 51 sprocket. Or i can lower the cylinder again or i can raise the cilinder.

So every one can say do this or do that but in the end you have to try to see how the bike rides like you want it.

Good luck.

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2/2/2018 12:11 PM

r18b wrote:

Not a pro

If i'm right you get with vhm 3 different insert to choose and a fourth to make ur own.
A- higher compression for hardpack.
B- standard compression allrounder.
C- lower compression for the deep sand.

First of all what kinda tracks do u ride and what kinda power are u searching for. What kinda pipe are you riding with.

Example. I did ride with pro circuit and a base gasket of 1.2mm in sand. It gives no bottom power.
Now i ride with a 0.6 base gasket in sand.
Now i have a new handbuild pipe so now i'm gonna try to see how this works with the .6 gasket. If the power is enuff from the bottom. I can choose to get back to 49 sprocket of go to a 51 sprocket. Or i can lower the cylinder again or i can raise the cilinder.

So every one can say do this or do that but in the end you have to try to see how the bike rides like you want it.

Good luck.

I use my CR for trails so I’m always on the hunt for bottom end power. When I bought the bike It had a Factory fatty on it and I really didn’t like it. I put the stock pipe back on and in my opinion it was much better. I run a 50 tooth rear sprocket and also have a Boyesen rad valve and Lectron Carb. The Lectron actually gave better results than expected. It added that low to mid don’t quit keep chugging along power that I was looking for.

The VHM head only came with one insert of my choosing. The way Langston power sports labeled them was (MX insert/SX insert stock or blind). I went with the SX for more bottom end. It’s nothing crazy but it’s higher than stock compression. I went with a slightly thinner base gasket but I didn’t want to make any big changes because I’m fairly new with making this kind of modification. I just want to know if I’m heading in the correct direction to get the desired specs that they suggest. I’m wasn’t sure if getting a thinner base gasket was the best wat. It my head the thinner the gasket the better chance of it failing.
Thanks.

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2/2/2018 10:19 PM

trow a 51 or 52 sprocket on it. if you using a thinner base gasket then standard then you should measure the squish to see what it is.Just in case you don't go to low. Yes the vhm with sx is the higher compression head. The pro circuit pipe did add for my feeling more bottom and a wider band then the standard pipe. With a cr250 you have to play it more with the trottle and clutch. In my opinion it does have more then enuff bottem power.

If it's not enuff bottom then you can go the way what a lot of people did and that's milling the cylinder. But always wondering why people did that.

So in the end, you're the one what only can say and do what is the best for your self.

Good luck

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2/3/2018 11:50 AM
Edited Date/Time: 2/3/2018 11:51 AM

Probably easiest to put on an FMF Gnarly pipe to give you bottom end if you don't mind loosing some top.
It's also a heavier gauge

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2/6/2018 11:39 AM

FahQ wrote:

Probably easiest to put on an FMF Gnarly pipe to give you bottom end if you don't mind loosing some top.
It's also a heavier gauge

I need to get one. I ran the PC platinum 2 on my 04 and really liked it and the gnarly is pretty much the same thing. I have the titanium 2 silencer so it makes sense to go with the gnarly. I disliked the Factory fatty so much that I put getting a pipe on hold. I’m starting to realize that there is actually a lot of difference between my 04 and 07.

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2/6/2018 1:00 PM

Could anyone tell me what the engravings mean? Is it from Factory like that? Maybe I just never noticed them before.
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2/6/2018 1:21 PM

The reason I ask is because I have a cylinder with no engravings and this one which I just got that has them.

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2/6/2018 1:30 PM

Have it on my cylinder to.. not the same ofcourse what you have.

So i thinks it a productionnumber or something like that. What else could it be.

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2/6/2018 4:00 PM

r18b wrote:

Have it on my cylinder to.. not the same ofcourse what you have.

So i thinks it a productionnumber or something like that. What else could it be.

That’s what I was thinking. Sorry if this turns out to be a long post, just a heads up. I’m sure if you seen my other posts you probably read about how I bought this 07 a little while back and some things just aren’t right with it. The bike itself was in a amazing condition but the engine doesn’t match. It literally looks like a crappy engine was out inside of a brand new rolling chassis. The frame swing arm wheels even radiators and hoses everything was brand new but OEM. Either great condition or OEM replacements. After getting the bike home I found how badly chewed up the engine cases are and the piston was beyond shot. This winter I was going to see what I could do to fix up the cases but soon found the cylinder needed some help when I started to tear down the engine. At this point I’m just seeing dollar signs. More dollars than what I planned on spending.

I found a complete 07 engine for sale, it looked good and is “supposed” to be low hours and original. I bought it hoping it would be my fix all. I just got it today and I must say it’s perfect. There may be 2 scuff marks on it, the inside of the cylinder looks like a brand new off the show room floor( sorry just excited). Point being the cylinder on this new engine has these engravings and even a serial number. The cylinder that came on the bike doesn’t so it must have been replaced. I really can’t figure out what they did or what happened to this bike. I’ve seen a lot of things but this one got me. Anyway, a year and a lot of money later I finally have the bike I want. Brand new factory connection suspension, new redone motor with Lectron Carb/ VHM head/ Boysen rad valve.... I can’t wait to get this thing in the woods.

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2/6/2018 10:38 PM

Good to hear that every thing is good now and you have the bike you want. Forget all the different pipes and play with the sprocket on the rear (51) for wood riding. That will bring you more then a pipe.
Yes, even the most won´t say it but as soon we see our bike we get excited. i´m one off those nutcrackers that talks to the bike lol
Enjoy the ride

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2/7/2018 5:09 AM

r18b wrote:

Good to hear that every thing is good now and you have the bike you want. Forget all the different pipes and play with the sprocket on the rear (51) for wood riding. That will bring you more then a pipe.
Yes, even the most won´t say it but as soon we see our bike we get excited. i´m one off those nutcrackers that talks to the bike lol
Enjoy the ride

Thanks for all the advice. I will hopefully enjoy the ride. I’m going to keep Honda 2 strokes alive in my group as long as I can.

P.S if anyone wants to buy a less than perfect CR250 engine, I’m your guy!!

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