[JimDirt]

I don't see how it could slip , with a new chain the tension on the chain would be too tight for it to be loose enough to skip even with the tensioner disconnected

But back to the locking up part

I am guessing you just put the tower back on , and then turned it over and it locked correct ??

If so , what i would guess is , behind the flywheel is a tab/retainer , it keeps the timing chain from completely coming off the crank gear when you remove the tower for valve adjustment , its possible that in manipulating the cam when removing it , that you slightly moved the engine (it turned over a little) , and in doing so , the chain got bunched up

Then you got everything back together , and then when you went to kick(by hand or with your foot) the engine , the bunched up chain , got forced into the retainer , and is now jammed , or it forced the chain off the crank sprocket , and that is locking it up , but it sounds like (as long as your 100% positive all the timing marks are on and the cam is in the correct orientation with the engine *lobes facing 2 O-clock position/facing rear*) , and there is no excess slack in the chain , you are looking at removing the ignition cover and possibly the flywheel to get it free again , but that is where i would look if all else is confirmed to be set correctly

[Tm85cc07]

The reason I ask about cam gear slip is because my timing jumped 4th gear high idle causing me to need the complete rebuild. Seems like cam lobes are more like 3 o'clock

[Tm85cc07]

****high rev (not high idle)

[JimDirt]

Did you replace the Chain GUIDES ?? , as they are a wear item as well , especially if your chain was worn enough to jump time ,(as well as the tensioner which you said you replaced) , as i mentioned if your chain has a kink in it allowing it to be slightly overlapped on the lower sprocket , it could have bound up , but no matter what , if the engine locks up , there are only a few things that can cause it

The timing chain bound up at the bottom

The timing off enough that the valves are hitting the piston

OR (if i remember correctly) though less likely , the 250 has a press on timing gear on the cam , if it has slipped/spun somehow , this would also make the timing off

OR , some part fell into the engine and is locking it up , that's about all that would cause a lock up that i can think or , most of which are timing related

The slash marks on the cam gear should be level with the head like this - - , and at that time the cam lobe should be facing 2 O'clock , and the other 2 timing marks should also be on their marks , if this is not the case , then something is off either in assembly or a issue with a part

[Tm85cc07]

Just received my new oem cam. Looks like old cam gear us spun 4-5 teeth. Thanks for the help!

[JimDirt]

Glad you found the issue , i know it has happened , that is why i mentioned it , though its kind of rare , but hopefully now you can get back to riding it instead of working on it !!

[Tm85cc07]

Still not running. However was much easier to shim valves. How do I test the compression?

[JimDirt]

You test it the same way you test it in a car , you screw in the Compression Tester Adapter into the spark plug hole , crank/kick over the engine several times till the gauge stops increasing and take the reading , , note that the compression will be under 100 psi (60-90)because of the Auto-De-Compressor , you would be better off doing a Leak Down Test instead (you need a Leak Down Tester) , as this will tell you if there is any issues with Valves sealing or bad rings , head gaskets , etc

What issue is remaining , that is preventing it from running ??

[Tm85cc07]

Not sure what the remaining issue is. I do have spark and everything is perfectly timed and shimmed. I am not familiar with a leak down test. Any idea where to find tools and info?

[Tm85cc07]

I am scared that while turning engine over with bad cam that I could have damaged the bran new head/valves

[JimDirt]

The only way you can damage any parts is if the timing was off , in which case that is the issue , if all marks line up (Notches on cam sprocket level with head like this - - , and the cam lobes are facing 2 O'clock *rear of engine* , and the timing mark in the small round plug on the ignition side , and the large round plug on the clutch side are all lined up at the same time , then it "should" be in time and you should have no issues turning it over

As far as the Leak Down Tester , you should be able to rent one from a auto parts store , just make sure it has the correct plug thread adapter , and you need a air compressor capable of holding up to 100 PSI (the pressure needed to perform the test) , you don't want to buy a Leak Down Tester unless you plan on using it a lot , they are not real cheap

You can get away with using this http://www.crfsonly.com/catalog/product ... ts_id/3701 , its cheap and will do the job , but it wont tell you what percentage of leakage you have , as some leaking is permissible but not excessive , usually any more than 20% means there is a issue , this hose will allow you to air up the cylinder , and you can listen to the air if its escaping , as you will hear it thru the muffler , intake or crankcase , but again , no telling how bad its leaking without the gauge setup that is part of the Tester

This is the Leak Down Tester Ken sells , you can find some cheaper ones on the internet , but this one is already set up for the bikes
http://www.crfsonly.com/catalog/product ... ts_id/1889

The one i have is made by Snap-On , but i have had it and used it for years on cars , motorcycles , jet ski's , boats , etc

[Tm85cc07]

Got her fired up just needed a new cam and sniff of stater fluid

[JimDirt]

Should not need starter fluid , did it sit for more than a month ?? , have you checked/cleaned the carb ??

If the jets are clean and the timing on , and it has FRESH gas (a few weeks old at most) , the bike should start without any external help from starting fluid , it should start within a few kicks

What is your starting procedure ?? cold and hot

[Tm85cc07]

Bike sat for 2 months. Gas is 2 months old. Used choke until she fired and then once warm purred like a kitten. Bike was backfiring when throttle was turned

[JimDirt]

Pilot Jet is clogged thanks to the Ethanol in the gas (also only use Premium gas 91 octane or better , 1 month is the limit with Ethanol based gas , it will work fine in your car or lawn mower , but not these bikes after about 1 month) , its best to just replace it , they are about $6.00 at the Dealer (or any bike shop) , this will cause hard starting and the popping