[Andy Salmonsen]

Hi, I am probably the dumbest 15 year old in the world for doing this but here we go.

A few months ago i noticed that my CRF250R 2007 had low compression when kicking it, my dad has an 05 and i did a good old hand test on the kick starter and mine was very easy to kick compared to his. A few months later when getting ready to ride the bike from a cold start, it started puffing white smoke out of the exhaust muffler for like 4 minutes like a 2 stroke. It doesn't puff smoke out like a 2 stroke anymore but when you rev it and let it settle back down to idle it will puff a little smoke out.

From all of that i figured that i could have some worn rings in the bike since it is old and i dont think it has ever had a top end done. I have a vertex piston kit and gasket kit so i am good to go for a piston, ring and gasket replacement. I am just wondering what i may be getting myself into here and wanted to get some advice. Is the smoke from say oil getting into the combustion chamber from a bad oil ring and the low compression from worn out rings? Or is it something like a blown head gasket for the smoke? I am worried about the compression coming from the valves, would the valves cause low compression and what could it be? Im a smart kid and am confident i could do piston and rings and gaskets, I'm just worried about something with the valves and want to get a little advice on that and the whole top end rebuild. Should i try to save up enough money to just bring it too a shop and have them do it? Please just give me a little advice on what you think i should do in this situation,Thank you.

P.S. My dad is able to help me with all of this, but he has never done anything like a top end rebuild so we are both new at this and looking for advice.

Please dont roast me too hard in the comments for being an idiot.

[Back2-2]

Hello Andy and welcome. First you actually sound like a bright energetic young man not a dumb teen. That's refreshing to an older guy like me to see.
Ok - White smoke usually indicates water / coolant being ingested. Blue smoke is oil burning and black is a rich mixture of fuel burning.
First thing is to get the factory service manual. With the manual and basic skills a top end replacement is actually pretty easy on these bikes. Yes, the piston and rings are probably due replacement and the valves are more than likely due for service and or replacement.
Many of us have went with the Kibble White valve job from Ken owner of this site. You do that and you can come close to never having to worry or mess with the valves again.
You can buy prepared ready to install complete heads or send yours in and have Ken take care of everything for you so all you have to do is install the head after the piston rings and cylinder go on.
You probably should do some trouble shooting before just diving in. A pressurization check of the cooling system will tell you if you have a blown head gasket and also inspect the coolants color to see if it has a brown color. Level of the coolant will also tell you if you are loosing / burning coolant. A engine compression check will give you some idea whats going on also. If you do a compression check and you see air getting into the coolant you know you have a issue.
Again, with a service manual you can do all this and do it yourself. It's really not much more difficult than doing a top end on a modern 2 stroke. There are several of us here than can help you if you have questions.

It's actually fun to learn and do the work yourself.

[JimDirt]

Welcome to the site !!

I agree with Neil on the diagnosis , and on the suggested solutions ..... You can do all the work yourself with the exception of the head work/valves , and the best bet to avoid needing to buy all the parts needed to to the job , then source it out to hopefully someone that knows what they are doing with these engines , as doing valves on these bikes require special tools that automotive machine shops do not usually have , as well as the knowledge to do the correct cuts needed to the seats ..... So a set up ready to go head is the best bet , and doing that will allow you to simply wait for it to arrive , then bolt it on and go .... , if you sent in your complete head , he can even bench shim it , so all you need to do is basically bolt it on , you won't even need to adjust the valves ....

If a machine shop that does not know how to correctly do a CRF head tries it , and cuts the seats too deep , you just ended up with a expensive paper weight , as you will not be able to find a valve shim to fit the wrongly cut seat , as the seat depth determines the height of the valve stem sticking out , which in turn determines the size of the shim needed , it would act just like the valves were worn down and you will have no way to correct it ..... , so whether you send your head here , or buy a ready to go one from here , or anywhere else , that would be your best bang for the buck .... , If you need any help in assembling or setting stuff up and you get stuck , you can find help here to guide you thru it , one of us is usually around ..................

[Andy Salmonsen]

Thank you all for the advice you have really helped me!!!'

I have the manual for the bike so Im good on that.
Unfortunately I already have the bike all torn down with coolant and oil drained so it is ready for the rebuild. When i did drain the coolant it was not brown. I have never seen air bubbles in the coolant. The only thing that does point to head gasket was after every 2-3 rides i would check the coolant level and it would always fall an inch or so. It could just be overflow but with the smoke being from said coolant i think that kind of narrows it down to a worn out head gasket which i have with the kit so will be good on that.

I have heard of a leak down or pressure test on the bikes to check for leaks just dont know how to do them. Do you hook and air compressor up to something that goes in the spark plug hole and then pressurize the chamber and listen for leaks? Should i even do a leak down test if I'm already gonna take the engine apart and look at the valves? If i did need new valves and say seats and shims how much would it be to send into Kibble?

I have already done a compression test and it came out to 50psi and 30psi on the two different strokes. I dont know how to tell the compression apart from one or the other stroke. The bike isn't hard to start so i think the shims should still be in specs but you never know.

The one thing that is really confusing me with the top end is taking the cam chain tensioner off. In the manual they say that you have to buy a certain tool for the job that basically looks like a fancy screwdriver. Ive read the people use just regular screwdrivers or macgyver a screwdriver that has no handle and vice grips. I also hear people just pull the whole tensioner off and dont worry about it. I DO NOT want to screw up my timing by using the wrong tool for the job and have myself in a hole I can't dig myself out of. Do i buy the special tool or is it that all i need is a simple screwdriver?

Thank you again for the support and advice your making my life a whole lot easier!!!

[Andy Salmonsen]

One other thing, How much do you think it would be to send in my head? Also if I were to purchase a had and "bolt it on" do i need to put my old cam in it or does it come with a came? Do i have to do anything to it because in the pictures it seemed as if it still required some assembly?

Thanks

[JimDirt]

Thank you all for the advice you have really helped me!!!'

I have the manual for the bike so Im good on that.
Unfortunately I already have the bike all torn down with coolant and oil drained so it is ready for the rebuild. When i did drain the coolant it was not brown. I have never seen air bubbles in the coolant. The only thing that does point to head gasket was after every 2-3 rides i would check the coolant level and it would always fall an inch or so. It could just be overflow but with the smoke being from said coolant i think that kind of narrows it down to a worn out head gasket which i have with the kit so will be good on that.

I have heard of a leak down or pressure test on the bikes to check for leaks just dont know how to do them. Do you hook and air compressor up to something that goes in the spark plug hole and then pressurize the chamber and listen for leaks? Should i even do a leak down test if I'm already gonna take the engine apart and look at the valves? If i did need new valves and say seats and shims how much would it be to send into Kibble?

I have already done a compression test and it came out to 50psi and 30psi on the two different strokes. I dont know how to tell the compression apart from one or the other stroke. The bike isn't hard to start so i think the shims should still be in specs but you never know.

The one thing that is really confusing me with the top end is taking the cam chain tensioner off. In the manual they say that you have to buy a certain tool for the job that basically looks like a fancy screwdriver. Ive read the people use just regular screwdrivers or macgyver a screwdriver that has no handle and vice grips. I also hear people just pull the whole tensioner off and dont worry about it. I DO NOT want to screw up my timing by using the wrong tool for the job and have myself in a hole I can't dig myself out of. Do i buy the special tool or is it that all i need is a simple screwdriver?

Thank you again for the support and advice your making my life a whole lot easier!!!

You could do a leakdown test , but it is a little difficult without the tester (I have had one since the early 80's , as they come in handy if you do your own work) , what a leakdown tester consists of , is a pressure regulator , 2 air pressure gauges , and a air adapter that allows you to screw a air hose into the spark plug hole , what it basically does is pressurize the internals , if there is a leak of any kind , you will get blow-by , for example , when the engine is at TDC on compression stroke , you pressurize the cylinder with say 100 psi , (this is best done with everything still intact like hoses and oil/coolant , etc.) , If there is a issue with rings for example , you will hear air in the crankcase , removing the oil fill plug would confirm this .... If the head gasket is blown , you would hear air (and see bubbles) in the radiator .... If the valves are leaking , you would hear air either thru the exhaust pip/header , or thru the carb/airbox ........ Follow ??? , so the Leakdown Tester is quite a handy tool

(This is what I have)





A 2007 CRF250R should have 57 psi at 800 rpm (basically kicking over the engine several times with a full throttle until the gauge stops moving) *using your foot not hand , just like when you are trying to start it , and just as hard of a kick*

The tensioner can be loosened and just removed , when reinstalling , you put it in till there is slight tension , then using a very short small flat blade screwdriver turn the screw to take away the tension , then push the tensioner in till its flush , then snug the bolts by hand so they hold the tensioner flush with the opening , then release the screwdriver , then tighten the bolts , then turn the screw again , then let it release , and it should be set ......

I made my own by cutting down a cheap screwdriver

[JimDirt]

One other thing, How much do you think it would be to send in my head? Also if I were to purchase a had and "bolt it on" do i need to put my old cam in it or does it come with a came? Do i have to do anything to it because in the pictures it seemed as if it still required some assembly?

Thanks

This is a basic price guide (scroll down to the head part , and also look at the part where it says Valve Jobs , on the first row of Engine Services) , you can contact Ken (the owner here and the one doing the work) and he can go over any specifics or questions you may have and what would work best in your situation and with your budget , his prices are very reasonable and the work is top notch ...
https://www.crfsonly.com/catalog/index.php/cPath/258

You will be reusing your cam and tower , he will replace/supply the head itself , unless he repairs/redoes yours , and the valves , etc. , the parts will vary with the cost ... , so basically you send him your complete head with cam.... or just the head itself and you will reinstall your cam and tower along with you shimming the valves once the new or freshened head is returned , if you send it all to him , he will do all the shimming and it will be ready to bolt on and go ....

[Back2-2]

The small cam chain tension tool you asked about is very easy to make. The service manual gives you the spec's and it basically a small "T". It works really well and like I said you can make one real easily. The small blade part turns the internal adjuster and the wider part of the "T" locks it it place to hold the tension while removed.

I recommend sending the head from your bike in to Ken. He will return it ready to go - plug & play. You will have to put the cam in but that is not a problem, just follow the manual. It is not cheap but it is part of the maintenance that these high performance 4 strokes require. One nice thing is that if you do have the head redone you won't have to touch it for a long, long time.

One other item I recommend you have to do this job is a torque wrench.

[Andy Salmonsen]

Ok, I have a torque wrench so I'm good there.

Gonna look into getting a leak down test kit to check the valves. I have the exhaust and carb off the bike right know so will that affect the leak down test or no?

My plan is to do the leak down test and check for leaks in the valves, if so i will probably send the head into
Ken. ill replace all the gaskets, check for damage to cylinder walls, check the crankshaft for bad wear. Then ill replace the piston and rings, hon the cylinder, put the head back on and be ready to rock and roll again.

I have been looking for the honing stones to hone the cylinder but have not been able to find them. Does anyone know how to find them and wear to buy them? If you do please let me know where you got them.

Thanks.

[Andy Salmonsen]

One other thing, what is a tower? If i sent my head in would i have to install the tower as well or will it already be installed?

[Back2-2]

DO NOT Hone the cylinder. You will destroy the Nikasil cylinder coating. Very lightly cross hatch the cylinder wall with a oil soaked
Scott-brite pad - that's all.

If the top end of the engine is still intact you can do a pressurization check. The "towers" are the cam hold down pieces. When you send it in to Ken you can have him do the whole job so all you have to do is bolt it down to the cylinder.

[Andy Salmonsen]

Ok, ill stay away from honeing it then.
Gonna purchase a leak down tester and go from there. Is there a certain leak down tester i should get or does it not matter?

[Andy Salmonsen]

https://www.ebay.com/i/184089862369?chn ... 7EEALw_wcB

Is this a good leak down tester or no?

[Aussiecrf230]

Hi Andy,
Did you have the throttle wide open when you did your compression test?

You don't need a store bought leakdown tester in a lot of cases. There nice to have, but if you already have an issue you can make one out of an old spark plug and an air fitting.
With the piston on TDC on firing stroke pressurise the cylinder with the radiator cap off and listen where the air leaks out. There will always be a small leakage past the rings due to the ring gaps. There should be no air leaking out the cooling system or out the inlet or exhaust. If you have the head off already if you turn it upside down and put some fuel in the chamber any leakage will show up in one of the ports.
I find the bores clean up well with some wd40 on the scotch brite pad and use it gently following the cross hatch pattern. If there is no cross hatch left or obvious damage that is another issue.

If you are going to all the effort of a rebuild including the head it will probably be worth the expense of a timing chain and tensioner as I assume it maybe worn.

[Aussiecrf230]

Hi again Andy,
If you did lose a little bit of coolant sometimes the waterpump seal is to blame.
If your engine oil when drained was not milky then it is probably not an issue.

As you said the lost may have been from overflow.
The white smoke can also be from moisture in exhaust pipe due to the humidity or washing down the bike.

If you can post pictures of the head and block faces the guys here should be able to spot if there was leakage of the head gasket.

Just trying to cover all bases.

Take it slow and ask lots of questions. Everyone here loves to help as we all love bikes.