[Bullvine rider!!]

I appreciate every comment and hope you didn't take my reply the wrong way. I was actually replying to hoser about the cam chain jumping.

No I didn’t, thanks. Im actually reading up on how to fix a spun cam gear hahaha. And most of the posts say the same thing “to get a new one” because rotating the cam, the shaft & wheel to get cam/gear in correct position is difficult and can throw off all of it plus timing. 🤷🏻‍♂️ Up shits creek.

 

[hoser]

That’s what I meant, the marks on the cam gear should be visible on the right and left hand side of the head when the motor is at TDC. They definitely aren’t and that’s why I feel the gear spun on the cam. Let me figure out how to post pics so you can see what I’m saying

This comment is why I kept talking about the chain. To say the motor is at TDC and not have the chain on and say the marks are off doesn’t really make sense. Not trying to be a jerk, just saying where I was coming from.

Compare the cam to pics online and see if it looks different. As far as an average Jo Doing this, it can be done, but even if you are off a degree or two it will change the way the motor runs. I personally wouldn’t risk it. You could call Web Cams and see what they would charge, but they are not a cheap shop. There are others like Crower that come to mind that could likely do it as well, but I have only used Web myself. Might just be a good time to throw an aftermarket cam in it. But as you are kinda mentioning, would definitely be best to pinpoint why it spun if it actually did. If your tensioner failed and skipped a couple teeth the resulting valve to piston contact could make it spin. There really is no other way for it to spin, something has to prevent that cam from rotating to make that gear spin. Personally for peace of mind, I would definitely pull the head, it will only cost you a head gasket.

 

[70oldsracer]

So, I get what you’re saying about TDC, but i laid the cam in the head approximately where it needed to be if the cam chain was connected and the motor was at “TDC”, just like as if I was setting the valve lash and the marks on the cam are way off. I also, put the cam in the head with the marks lined up with the head and the exhaust rocker arm is hitting the decompression lever, which is obviously wrong. As far as why this happened, I agree with you 100%. The tensioner failed, the chain jumped a few teeth and a valve hit the piston causing the cam to lock up and since the chain continued to turn with the crank, it spun the gear. My leak down test showed little to no leakage, so I don’t know how, but I don’t think a valve bent. I ordered a new OEM cam and will probably pull the head for peace of mind.

 

[CJM]

This comment is why I kept talking about the chain. To say the motor is at TDC and not have the chain on and say the marks are off doesn’t really make sense. Not trying to be a jerk, just saying where I was coming from.

Compare the cam to pics online and see if it looks different. As far as an average Jo Doing this, it can be done, but even if you are off a degree or two it will change the way the motor runs. I personally wouldn’t risk it. You could call Web Cams and see what they would charge, but they are not a cheap shop. There are others like Crower that come to mind that could likely do it as well, but I have only used Web myself. Might just be a good time to throw an aftermarket cam in it. But as you are kinda mentioning, would definitely be best to pinpoint why it spun if it actually did. If your tensioner failed and skipped a couple teeth the resulting valve to piston contact could make it spin. There really is no other way for it to spin, something has to prevent that cam from rotating to make that gear spin. Personally for peace of mind, I would definitely pull the head, it will only cost you a head gasket.

exactly.

as i said before-its not a smart idea to try and fix the cam and even more so its a good idea to find out why it spun.

side story

i go to glamis like every year (or did for several years). for me to go costs A LOT. we pay a dude whom trailers our stuff out, we fly there, rent cars and campers, etc. I get there and i let a friend ride mine and it locked up..literally first day were there..in camp. valves met piston (we discovered when taken apart).

tensioner failed and funny thing is-it was literally a new build with like less than 20 hours on it and properly broken in and such. we to this day do not know if the cam spun (hotcam 3) but dont want to chance it and bought another one. I never paid to check it, nor do I really want to know..i just have the old one sitting there. the exhaust valves met the piston, they broke off at the head of the valve and went thru the engine. catastrophic failure...

I will NEVER use the stock tensioner again.. im using a tokyo mods manual tensioner..it cant fail unless i dont adjust it. this is the 3rd spring loaded tensioner I have seen just fail. a buddies 400ex (lucked out no damage) and a prior one for my 450r RIGHT before a glamis trip.

 

[70oldsracer]

exactly.

as i said before-its not a smart idea to try and fix the cam and even more so its a good idea to find out why it spun.

side story

i go to glamis like every year (or did for several years). for me to go costs A LOT. we pay a dude whom trailers our stuff out, we fly there, rent cars and campers, etc. I get there and i let a friend ride mine and it locked up..literally first day were there..in camp. valves met piston (we discovered when taken apart).

tensioner failed and funny thing is-it was literally a new build with like less than 20 hours on it and properly broken in and such. we to this day do not know if the cam spun (hotcam 3) but dont want to chance it and bought another one. I never paid to check it, nor do I really want to know..i just have the old one sitting there. the exhaust valves met the piston, they broke off at the head of the valve and went thru the engine. catastrophic failure...

I will NEVER use the stock tensioner again.. im using a tokyo mods manual tensioner..it cant fail unless i dont adjust it. this is the 3rd spring loaded tensioner I have seen just fail. a buddies 400ex (lucked out no damage) and a prior one for my 450r RIGHT before a glamis trip.

So, I’m definitely buying a manual tensioner, I’ve heard of and read to many stories of the oem one failing and ruining the motor. I’m am sure you saw in my post, I bought a new OEM cam. I am not going to try to fix the gear on the one I have, but if you laid your cam in your head after you had the catastrophic failure, I’m sure if the gear spun, you’d be able to tell if it spun as bad as mine did. I’m going to pull the head, but I’m almost 100% sure the rest of the motor is okay. The motor spins over freely and the leak down test showed no leakage. I’d find it almost impossible to have a bent or broken valve and have no leakage or lock up. Keeping my fingers crossed and I’ll let you know what I find when I pull the head off.

 

[CJM]

hey worth a shot to take a look to be sure its good right?

tokyo mods has the nice manual tensioners, I and all my buddies run them with no issues

 

[hoser]

hey worth a shot to take a look to be sure its good right?

tokyo mods has the nice manual tensioners, I and all my buddies run them with no issues

I wish they made them for the 04-05. Not sure why they don’t. Maybe the stock first gen tensioners are more reliable??? I’ve never had one fail or seen one fail for that matter.

 

[CJM]

I wish they made them for the 04-05. Not sure why they don’t. Maybe the stock first gen tensioners are more reliable??? I’ve never had one fail or seen one fail for that matter.

hmm since having an 06 for years i never noticed they dont have them for the older engines.

i wonder if there is a difference, tensioner is a tension and so long as it fits and dont leak i dont see why it wouldnt work. i know the tokyo mods one is really for a crf engine, but it fits fine

amazon and one from ape sold at jsd look super similar here

Timing Cam Chain Tensioner Manual Adjuster Fit for Honda TRX450R TRX 450R TRX400EX

Buy Timing Cam Chain Tensioner Manual Adjuster Fit for Honda TRX450R TRX 450R TRX400EX at Amazon. Customer reviews and photos may be available to help you make the right purchase decision!

www.amazon.com

APE Racing Manual Cam Chain Tensioner (04-05 Honda TRX450R)

[email protected]

jsdmachineworks.com

 

[hoser]

The bolt patterns are different between the two generations. I just like some of the Tokyo Mods stuff and wish they made on for the 04-05. I‘ve used APE stuff in the past and it’s decent stuff, but yeah that tensioner looks just like the eBay specials, which I don’t love lol.

 

[Bullvine rider!!]

Doesnt the 1st gen have a longer tensioner then 2nd gen?

 

[Bullvine rider!!]

Doesnt the 1st gen have a longer tensioner then 2nd gen?

Longer bolt it looks like. Maybe thats why they hold up better 🤷🏻‍♂️.

 

[CJM]

The bolt patterns are different between the two generations. I just like some of the Tokyo Mods stuff and wish they made on for the 04-05. I‘ve used APE stuff in the past and it’s decent stuff, but yeah that tensioner looks just like the eBay specials, which I don’t love lol.

gotcha. yea its been some time since i looked at once of them older engines.

im sure that you could literally hollow out a tensioner and make one, its fairly simplistic

 

[Bullvine rider!!]

Questions: with the manual tensioner’s, how do you determine the chain is loose? And how do you determine how tight it should be adjusted? Please excuse my wealth of knowledge 😄

 

[70oldsracer]

hey worth a shot to take a look to be sure its good right?

tokyo mods has the nice manual tensioners, I and all my buddies run them with no issues

Well, I pulled off the head and the cylinder, I figured if I had the head off I might as well pull the cylinder and check the piston and rod. So as you can see from the pics. the valves definitely hit the piston. Both the piston and valves look fine and so does the crank. The head gasket looks like it might have been blown, but there was no water in the oil and that didn't show on the leak down test. I'm going to pull all the valves and spin them in my lathe to make sure none of them are bent. So I'll clean everything up, put new gaskets, valve seals, cam, cam chain and tensioner and I should be good to go. Thoughts on this top end gasket kit, I know its cheap.

Top End Gasket Kit fits Honda CRF250R CRF 250 2008 2009 by Race-Driven

Top End Head Gasket Kit fits Honda CRF250R CRF 250 2008 2009 by Race-Driven

www.race-driven.com

 

[CJM]

well there ya go

spend the coin on oem or cometic at least or even tusk from rocky mountain

 

[Bullvine rider!!]

Go all out while your in there, its tax season 😆.

 

[hoser]

Personally, I would not use those valves. have you ever looked real close at a valve that’s made contact? There are little cracks at the base of the valve, and it doesn’t take long for those to turn into a broken valve. I’ve seen it and experienced it. It’s not worth the risk. It sucks, it it sucks much less putting new valves in it now versus an entire top end and head. And as @CJM said, go for OEM or Cometic gaskets.

 

[hoser]

Here’s a pic of what I’m talking about. This valve IS NOT from a motor I built lol. It was barely bent, I can’t even see a witness mark on the face of the valve, but there are lots of cracks at the base of the stem.

 

[70oldsracer]

I received the new cam and you can clearly see from the pics that cam gear spun a decent amount. When the lines on the cam are parallel with the head, the lobes are in very different locations. I also pulled the valves from the heads and they are indeed bent. I spun them in my lathe and some are bent as much as .015”. I ordered 4 new Kibblewhite valves, spring kit and seals. I need a place that can cut the new seats that’s not going to cost me a fortune. Anyone have any suggestions? I’m in Queens, NY, I don’t know of any local shops. I checked the piston and cylinder and everything is within spec, so I’m going to reuse them. I may buy the cylinder works

 

[70oldsracer]