Duneaddict,
Sorry to hear about your k-boom. It also sounds like you might be comming out of the closet with the thump thumps. I like the 450 also. In fact I have a post somewhere on here asking about the two. I think I want the motor durability of the DS (possible boat loads of NOS in the future?).
I do think the Nicasil bore is worth its weight for heat transfer. That and my little heat exchanger treated me pretty good. Remember too that I was over revving that thing to 8500. Over rev makes tons of heat. That reminds me, your right about the 7200 sugested rev limit. Since your making a race motor, consider a little higher. Mine was a trail machine and I ran that pipe for over two years. Just a little reference idea.
Also, the piston. The problem with the KX is that it only comes 86mm. Wiseco makes them bigger but I like cast better. I think I was looking at a YZ 490 for a big bore full circle piston. I'm not sure.
About coolant flow in the bridge. I don't think you need to dig out books. As long as you can get some coolant to pass through you will be better than nothing. Alot of Yamahas rely on natural convection to circulate water through cylinders. Look how well just drilling oil holes in the piston helps.
Tom,
Back to your post. For gains on a 250 or 500. Reasonable type work for trail use, I think you will get more gains with the 500. But only to a point. You have to remember the 500 is a toilet stock. With good porting and pipe I think 60 is about right. About a 15-18 hp gain. Now the 250 I think will only realize high 40's. About the same as current dirt bikes. About a 12-15 hp gain. I guess they are pretty close. Like everything, it depends on how much work you want to put in. You asked about just installing a pipe. I definitely think the 500 because the stocker is poop. The problem is the after markets are worse. I guess that last statement changes my answer don't it? I have heard the LRD pipe works. I also heard you can't get one. I don't know what to tell you now. I think I'm going to quit while I'm ahead. Sorry.

 

Duneaddict,

Would you mind commenting on the power characteristics you noticed on the FMF Gold Series as opposed to the FMF Fatty on the LT500. I have a Gold Series myself and as is appears to be much like the Paul Turner, I was going to keep it as the LRD is not availble. I plan to port it moderately for an all around type powerband (60HP or so max).

Thanks

 

Thanks guys. I just bought a used LRD pipe so I hope that it is all it is supposed to be. I do have to build a silencer for it though.

Duneaddict, sorry to here about the LT. If you don't mind I would like to know the details of what the damage is when you get into it, and what the symptoms were before it happened. Just so I can recognize any potential problems in the future. I do have an automotive temp gauge I plan to try to make work. Not sure if I want to try and make a spacer to fit between the water pump cover and the connector, as it is called in the online microfiche, so that I can mount the sending unit. Or make a t-fitting to mount inline on the hose, sort of like one of the inline coolers that's being sold.

To change topics, does anyone have any suggestions on removing the head studs? These things are being stubborn. I have only got two out so far. I may have to weld the nut to the stud if nothing else works.

 

Oh goodie!!! Someone else besides me toying with NOS! I have plans to put the big yellow bird on the bottle next summer. I'll be doing a bunch more research this winter on the above discussed topics.
I'll agree that the motor durability is well proven with the DS, but I sure like the thought of that light weight Yammie... even if a little reliablilty is sacrificed...
10# ~= 1HP... Gosh, If I just went on a diet....

Tom, where'd you get lucky enough to find an lrd???? I have a used one also, but haven't tried it yet. I will also face building my own silencer/stinger.

The diff b/w the gold series and fatty are substantial... and are merely a 'seat of the pants' estimate.
The GS is hardly an improvement over stock... The fatty makes pretty decent power over and above the GS, but I don't really have a good comparison for you... There is hardly any visual differences, other than the fatty is a bit thicker..

I'll keep ya'll posted when I get the bomb disassembled... probably won't be very soon, as I'm right in the middle of a Honda rebuild right now.
But I can tell you what happened.... TOO MUCH HEAT! I ran the hill too many times, and didn't have a coolant temp gage...
There is an outfit called Warp Drive or Warp Speed... something... I met the guy at the dunes this year. He's out of Kansas. He builds/sells temp gages fairly cheap.. You could get away with the sending unit type, but I'm always watching my weight, so keep that in mind.
I'll mount mine right at the pump inlet, so I can look down and see it easily.

Stud removal tool, or double nut... sometimes they can be a real bugger.

Regards,

 

Got lucky on ebay. A guy was selling a chromed cylinder and some other parts. In his description he mentioned he had some more parts including an LRD pipe. Emailed him and made the deal. Called LRD to see if they had a silencer, which they didn't, but they did sell me some bends and some tubing to try and make it.

 

wow, you got lucky... that's where I found mine too... it's got some dings in it, and no silencer either, but at least I have one...

Once I get my motor back together again again, I'll try it out in comparison with my homemade job.

Regards,