[cristianosolo]

Recently , maybe 2 weeks ago , become very very difficult to start the CRF 250x 2005.....before was starting very well with elittric start.....right now is very difficult to start....more than 20 kicks and many times i start down hill......
When is very very hot, just after turning the bike off, the bike start very well.....as soon you wait 10 - 15 minutes is difficult to start the bike...
Important information:
- i just cleaned the carburator , the air filter....the gas filter is new.
-Battery and elictric start working well until 2 weeks ago.
-Kick start working well until 2 weeks ago
-SPARK PLUG new but get dirty very very fast.....i see it oily....tomorrow i will check again, but last time was oily
-is using some oil ....not much but i have to add some ....
-the pistoN is quite old. I just order a piston Kit but i have to wait a month. I will change the piston , but i'd like to know if is something different....
- BUT THE BIKE RUN PERFECTLY, NEVER LIKE BEFORE ....ONLY THE STARTING IS A BIG PROBLEM...
thanks

[JimDirt]

I am guessing your intake valves have tightened up , you need to check the clearance and see if its tightened up , if it has then that is the issue

[cristianosolo]

thanks man .....other people told me the same...
sorry but i never did this work. I check some video and i think i can do easily but let me see if i understood well....

1) open the head, check the clearence. if is fine the proble is another.
2) if is not fine like the manual say, how can i change it?
3) i understand that i must open the valve and just down there is a little disk called SCIM that i have to replace, change to get exclacly the hight

i live in Nicaragua. I hope i can find the scim

thanks for the help....saludos Cri

[cristianosolo]

sorry..... SHIM is the name, not SCIM

[JimDirt]

Remove the valve cover

Remove the small round Allen Plug on the Ignition cover (left side)

Remove the Large Round Allen Plug on the Clutch side of the case (just behind the water pump)

Remove the Spark Plug (so you can crank the engine over more easily)

using your hand on the Kick Starter , slowly crank the engine over till the 2 marks that are on opposed on the cam sprocket are aligned with the top of the head (it will look like this - -

The cam lobes should be facing the rear of the engine at about the 2 O-Clock setting , like this /

Now check the other 2 marks (both plugs will have alignment marks with the case , one on the FLywheel(left side) , one on a gear (clutch side)

If all marks are aligned with the marks , then take a feeler gauge and slide it under the cam lobe between it and the bucket , your hopeful measurement will be

Intake(under the cam lobe) 0.005 in. +/- 0.001(0.12 mm +/- 0.003 mm)
Exhaust (under the FORK facing the front of the engine) 0.011 in. +/- 0.001 (0.28 mm +/- 0.003 mm)

Report back with your findings

[cristianosolo]

Thanks man. I will....
Tomorrow is the day ....
Saludos

[JimDirt]

No problem , Glad to help !

[cristianosolo]

I could not find the tool to check the valve....in Nicaragua is very difficult to find parts....maybe tomorrow....i am going to the capital to see if i find it....i will let you know....saludos Cri

[JimDirt]

Try checking at the dealer , they should have the tools you need for sale

[cristianosolo]

finally i have the measure:

Looking the bike from riding position:

Intake right valve: very close, less than 0.04 mm (less because the smaller i have is 0.04 mm and it not goes inside)

Intake left valve: 0.15mm

Exaust left valve: 0.23 mm

Exaust right valve: 0.25mm

In my opinion the Intake right and the exaust left are not good....

what i do now? I was thinking to buy a SHIM case and change the SHIM. But, as i need 1 months to have it here, do you think i can ride the bike or better not? i dont want to broken the valve..............................................................................................................................................
:

[JimDirt]

Yea you can ride it , but it will need to be shimmed , BUT , even after the shim its not going to last long , a few rides (2-20 rides , but no guarantee) before it will need the valves replaced , so no matter what you need to decide how you want to do it , either by getting a used head on eBay and hoping its good and lasts , or having yours repaired , or buying a new head ready to bolt on and go ride

If you want to do the work yourself (everything except the machining) , then go ahead and get the shim kit and the correct feeler gauges (like these) http://www.crfsonly.com/catalog/product ... ts_id/5034

then while your riding it for now , you can start ordering everything you need or start saving and either ship the head to Ken , or if you can get a local place to do it properly then do that , but either way , you will need to replace the valves and have the seats cut , or just get a replacement head shipped ready to bolt on
http://www.crfsonly.com/catalog/product ... ts_id/3169

The nice thing about the CRF's is you can "bench shim" the head , so it does not have to be on the bike , you can literally shim it on the work bench , (or you could have Ken do it if you went the route , but he would need your cam and tower and buckets along with the head to do that)

Going with the setup i linked above , you could probably go a few years before needing a re-shim (i have been 9 years on my 450X since going Stainless without a adjustment needed)

[cristianosolo]

My idea is Shim the valves first ( can i shim one time only or when they need i shim again and again and again )

right now i can Order the new valve and make the work by myself with some friends. I'd like to learn how to fix this bike. The are many videos in you tube that can help...More here there is a mechanic friend of mine that knows something more than me. Do you think is possible?

Recently i ordered a new piston and the idea is to change valves and piston at the same time....
But as i live in Nicaragua i have to prepare well so....

i imagine that i have to buy a Valve kit like this one:

http://www.ebay.com/itm/NEW-GENUINE-OEM ... 6d&vxp=mtr

SOMETHING MORE THAN THAT?
or can i buy only the valves ( is cheaper ) ? but for sure i need the spring too....I MUST buy something perfect for my bike because from Nicaragua i cannot sen it back to change it if is wrong.....


thanks for the help

[JimDirt]

Yes you can as i said , go ahead and shim , and start ordering parts

You can do it yourself with the correct Valve Seat Cutting Tool , but be warned , if you cut too deep or use the wrong angles or tool , the head will need to be replaced or the at the least you will need the seats replaced

Doing both at the same time is the smart way to do it , since it will be apart , might as well do both

I personally would not go with that Honda kit , i would go with Stainless Steel kit , the stock Honda valves are Titanium and will go out again just like these you currently have , the stainless will last 5-10 times as long for the same money , if you get the set WITH springs then no need to worry , then everything will match

Just make real sure your mechanic friend is fully capable of doing the seat cutting correctly and knows how to use the seat cutting tool , it must be a tool made specifically for these 4 stroke motorcycle engines , the automotive cutters will NOT work , they are the wrong angles (there are several angles to the seat that need to be cut) and sizes

Be prepared to spend lots of money on the cutter , i personally feel it should be left to someone with a CNC Valve Seat Cutting Machine rather than hand cutting , too many chances for a costly mistake , and having a professional do it will be way cheaper than buying the tool , in fact , you can rebuild the engine and replace the head with a new one for the price of the tool alone

http://www.amazon.com/Neway-Seat-Cuttin ... B0009RJJTW

[cristianosolo]

I cannot buy a valve cutting tool, but i think that here in Nicaragua there are many workshop doing it with electric machine....

I was looking this video : http://www.youtube.com/watch?v=MZyMFpFZ ... ata_player
He is using grounding paste and sucktion cup to ground the valves : looks like easy and good. Whatdo you think?

Another question: when i change valves do i must ground them always or could be that they fit exacly without grounding?

If i will use a valve cuttin tool , which is the angle? Only one angle?
I saw a you tube video for a honda cb750 where they use 3 angles...

Thanks Cri.

[JimDirt]

No , absolutely do NOT hand lap the valves , it will ruin the face , these are not like automotive valves and that is why its best to send it to a shop that has a good reputation for doing modern 4 stroke valves , you will destroy the new valves if you do that , the valve face needs 3 angles , and it is usually done by a machine set up for these motorcycle heads , the drill tool i linked , is for someone that has experience and/or can experiment on junk heads till they get it right

If your local machine shop does not have experience doing these heads , then DO NOT take it to them , it will be ruined , just because they can do a car head , does not mean they are set up to do these heads , they are completely different in material and how they need to be machined , the valves themselves are very very soft , compared to automotive valves , and that is why they can not be machined and lapped in the same way

You can not "lap" them by hand , the valve material is soft and it will be like putting in worn out valves and they will be back to zero within a very short time , the seats have to be machined to match the valve face without cutting too deep , if the seat is cut too deep then the shims will no longer fit and the head will be junk , since the deeper the seat is cut , the more the valve sticks out and the smaller the shim will be needed , if they are at the limit then you will not be able to get a shim small enough to fit

Ken (the owner of this site) can ship to Nicaragua , so he can take your head and re-do it properly , and even with shipping , the quality of the work will out weigh the cost

Or you can go on eBay and buy a used or rebuilt head and have it shipped to you , the issue is , you can't just slap it together with some valves and hope it works , it has to be done by someone that knows what they are doing , with all the things i can do on a motorcycle , i send out my machine work to places that know what they are doing and have a reputation for doing the work correctly , if that is not done , then your just throwing money out the window , and it will cost much more in the long run

If you don't have any place that is reputable (with doing these heads) in your area then you will have to ship it somewhere , or just buy a new complete head and have it shipped to you , then just re-install it and your done , but this is not a thing you can slap together , it has to be done correctly by someone that has experience with these heads and valves and had the proper tools to do so , find out where the local dirt bike shops in your area have there machine work done , then contact them

I think your best bet here is to PM Ken and see what you can work out and go that route , saving money is one thing , but trying what your trying to do will cost you much more in the long run and you will be very unhappy with the results , you don't have to go with Ken , you can go anywhere that is reputable , but , it needs to be done right , and then you can spend the rest of your money on gas , riding ..