FXR150 camshaft/head issues

[Damien_Toman]

Yes, Sketchy, I was also thinking about just leaving some space in the mid-cam area and then Dwight from Leading Edge Cylinder Heads said he had discussed it with Richban's expert (on cams) bro' - it turns out that we all think it will work fine without the mid cam-shaft support. I am waiting on a reply about pistons from the site Richban listed. Once confirmed, I'll be ordering a new oversized piston, new valve springs and then have the cam modded by Richban's bro' (via Leading Edge). All costs a bit but while it is apart I might as well try and make it faster .

I have to admit that I think I caused the cam/head problem when riding back from ChCh after picking up the bike in Oct 2009. I was in Napier to try Roy's Hill on my way home. It was the Napier-Taupo road close day - due to heavy snow! With Roy's hill cancelled, I filled up with fuel (forgetting to check and top up oil) and headed for Taupo through heavy sleet. It was a survival exercise and I felt the engine tighten up on me a few times but just eased off - if I had stopped it would have been dangerous - I was wet and numb with the cold. The road was closed two hours later due to deep snow. When I checked the oil level in Taupo it did not show in the viewer. I filled it up, rode to Auckland and started bucket racing soon after, changing the oil after every meeting.

[Detlev]

hi there Damien just had a inlet cam cut got the specs from Japan it was 234 degrees duration 7,8 mm lift,when I ran it with my gn 250 carb had no midrange when i ran it with standard carb and airbox the bike ran pretty good,have to play with the gn 250 carb now to get it to run properly.

[Damien_Toman]

Hi Detlev. Interesting. Timing and jetting are both likely to need tuning after the cam change (from recent discussions I've had - I'm no expert). I've ordered a standard +2mm piston kit. Hope it arrives soon. My cylinder will then be rebored to match. I'm having the cams modified to provide more lift and longer valve opening duration (I think ). Did you leave the exhaust cam as standard? Might that be an issue?

[Henk]

Damien, you'll need to downspec the cams and reduce compression with a 5mm spacer under the barrel to get the most out of the extra 2mm. Trust me on this.

[Detlev]

Hi Detlev. Interesting. Timing and jetting are both likely to need tuning after the cam change (from recent discussions I've had - I'm no expert). I've ordered a standard +2mm piston kit. Hope it arrives soon. My cylinder will then be rebored to match. I'm having the cams modified to provide more lift and longer valve opening duration (I think ). Did you leave the exhaust cam as standard? Might that be an issue?

Hi there damien i was advised to leave exhaust cam standard .How does one change the timing?
Would it make sense to slot the cam to adjust timing?

[Damien_Toman]

Nice one, Henk. You couldn't write that with a straight face .

I suggest that a little time investment in the garage, with your extensive engineering skills, might lead to more fruitful results for you going forward . What was that score? ... while the competition had cam/head seizure issues .

Hope I can have it ready for Mt Welly 15-16th May. The piston is coming from Thailand and the cams are being done in Christchurch. I might end up just taking photos!

Have you got your engine back together yet?

[Damien_Toman]

Hi there damien i was advised to leave exhaust cam standard .How does one change the timing?
Would it make sense to slot the cam to adjust timing?

Hi Detlev. I will have to ask that question too, once I have the bits back. I'm not even sure if only my inlet cam is being modified - like I said - I'm no expert. What does "slot the cam" mean? Richban knows all about this FXR tuning and he is also very helpful. Maybe he will respond.

[Henk]

Still running on the borrowed motor since my "extensive engineering epertise" blew up my one, and I can't beat you if you're not racing (and not often enough at the moment when you are).
Sloting the cam refers to making slots in the cam drive sprockets in place of the standard holes so that you can vary the cam timing. Can give gains but make sure you mark the standard position when you get it done so that you have a known start point. Gary Johnson had this done on his GL145 and with no datum had a bit of a job to start with getting to a decent base position.

[Damien_Toman]

Hi Damien
Looking at your pics of the cams reminded me of the late 80s honda XR250RE heads
The would wear and you would have to fit Teflon half shims to guide the camsaft

Just wonder if this would be a cheap fix ?
Could work as your "test head " because you could port and mod the hell out of it without worrying to much

Just an idea

Sounds like a great idea but still tricky to do. We will go with a space and see what happens. It is the easiest and cheapest option. Thanks for the suggestion.

[Bert]

Not really up to the play on 4Ts but i did find this site a while back when hunting for honda CRF parts:
http://www.faliconcranks.com/sprocket_price.html
looks like it wouldn't be to hard to make a adjustable cam ?? if one had the required tools
http://www.hksusa.com/images_products/2613.jpg

[Damien_Toman]

Odd that its on the low load side, as the camfollower buckets would push the cam against the cam cover not the head, but the head is the hotter side.

What is the oil temperature?

Is the problem with the cam/head brg due to the oil getting really hot? would increasing the size of the oil cooler or adding another one help here?

What about ducting some air to it, and/or has removing/changing the front fairing reduced the air flow to the original oil cooler?

Unfortunately the engine does not have even a simple a temperature guage. The problem was most likely caused by low oil level - see my reply to Sketchy.

[Arronduke]

Damien.... are you looking at higher compession or porting the head?

Scary stuff... I look forward to seeing what you end up with before I blow mine up.

New heads and cylinders arn't a dime a dozen... on trade me.

I am definatly pulling mine apart to see how it looks.

I have a parts book if that helps? its a photocopy so it would be easy to copy.

[Damien_Toman]

Hi Arronduke. Yes, I'm aiming for higher compression and improving inlet and outlet flow. Leading Edge Cylinder Heads will do the work. Yes, the parts book would be awesome. Could I borrow it for a day? I've tried everywhere to buy a service manual but none are available. I'm on 0274 990 708. Thanks. Damien.

[Damien_Toman]

Still running on the borrowed motor since my "extensive engineering epertise" blew up my one, and I can't beat you if you're not racing (and not often enough at the moment when you are).
Sloting the cam refers to making slots in the cam drive sprockets in place of the standard holes so that you can vary the cam timing. Can give gains but make sure you mark the standard position when you get it done so that you have a known start point. Gary Johnson had this done on his GL145 and with no datum had a bit of a job to start with getting to a decent base position.

Hmmm. Sounds way too hard. I'll wait till all my bits are ready and then ask about assembly!

[Damien_Toman]

Not really up to the play on 4Ts but i did find this site a while back when hunting for honda CRF parts:
http://www.faliconcranks.com/sprocket_price.html
looks like it wouldn't be to hard to make a adjustable cam ?? if one had the required tools
http://www.hksusa.com/images_products/2613.jpg

Hi Bert. Excellent links. Thanks for that. Hmmm. So much to learn. I like the sound of adjustable cam timing. I also ride a CRF (250R) - no doubt you have already discovered www.crfsonly.com. I've bought heaps from them. Great service.