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Hey Tryce....lets talk motor!!!

9 posts in this topic

I talked to Ron while you were in IL this week. He is telling me to not port the head and run stock compression. As we all know, the Yamaha head is tougher to do and more $$$ for many reasons. I have so many questions I was just sitting here for a moment confused about were to start! The confusion comes from me talking to a GREAT tuner(you) and a GREAT motor builder(Ron) and asking the same question(What to do to get 55-58HP) and getting two pretty different recomendations. I know we are all learing about these newer 450's(me esspecially) but I thought I would get almost the same recomendations from you guys. The carb mod and the cams are the one thing we(you and Ron) agree on, oh yea, and good race fuel. The porting and the compression is were I get confused(happens pretty easy, lol). I took it upon myself to call Terry Varner...I got some kid that kept having to ask somone else every question I asked. The "kid" told me he would "start" the porting, but Terry USAULLY finishes it :devil:. I called Supertrapp. ...WOW, They didn't have a clue what I wanted. I asked for a ST slip on, and the said he has a dirttracker in the back, he'd ask him...he called me back and said the "dittracker" told him to tell me to buy a White Brothers pipe :lol:. Got know were there either. I told him I wanted a ST slip on for an Harley XR750...he said he would fax me his cataloge(which I never got) and I could buy what I needed :thumbsup:. All I'm tring to do is make/build a nice ice racer to compete in the pro class and I'm feelin' like I am spinnin' my wheels..BIG TIME!! I have the money..I have the desire..I've lost 40lbs. to prepare to be a competitive flattracker/ice racer...I just need some direction. 48 HP aint gettin' 'er done in the pro class around here. I'm done babbling. Can ya help a dude out?? :awww:

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Chris, I am confused why Ron leans away from head porting and compression. I just got a head back from Varner...stock valves...I will be putting it on tomorrow and on the pump this week sometime. I love my RHC head, but ya need a spare. I know the Hi comp is good for 2hp by itself.

As far as the right pipe, when you call ST you need to talk to Ted Bradley...the pipe you are looking for is not in the catalogue and few at ST even know of it. It is referred to as the 450 "kit".

PM me a number and I can call you after 9 when the minutes are free(I'm Cheap)

When you call Varner, ask to speak with him directly.

With the Carb mod, Pipe, 13.5, fuel, and cams you should have no problem hitting mid 50s. The ST pipe doesnt gain much more HP than some of the other pipes, it just holds the hp higher on over rev.

I will have to call Ron and see what his thoughts are...

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FFR, I'm interested in talking about the "carb mod" that you are referring to. I went to the dyno yesterday with 3 different bikes, a 262cc 250F, the 459cc 426F, and the 468cc '03 450F with some interesting results.

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36 HP from the 262

46 HP from the 459

53 Hp from the 468

the 262 & 459 were way rich on the pilot & needle which caused a significant dip in the air fuel ratio. My question to you would be...how much HP (peak) can this affect. The other obviously is the numbers generated by the dyno as I've only run CRF & YZF 250's before and they basically would put out around 29/30 HP in stock configuration. I did have a stock 450F going but he dropped out at the last minute. It would have been good to have that data as the 426/459 easily runs with and or away from stock 450's..... :thumbsup:

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36 HP from the 262

46 HP from the 459

53 Hp from the 468

the 262 & 459 were way rich on the pilot & needle which caused a significant dip in the air fuel ratio. My question to you would be...how much HP (peak) can this affect. The other obviously is the numbers generated by the dyno as I've only run CRF & YZF 250's before and they basically would put out around 29/30 HP in stock configuration. I did have a stock 450F going but he dropped out at the last minute. It would have been good to have that data as the 426/459 easily runs with and or away from stock 450's..... :thumbsup:

My dyno shows the stock 450s at about 48hp. At what rpm was the dip? Was this dip in the a/f on a WOT run? If so, it has nothing to do with the needle or pj, but rather the pipe. As the MJ is a constant, any variation in the A/F curve is caused by a change in VE(volumetric efficiency). This is a good way of telling just how good the design is of the pipe you are running.

On my dyno screen, I have made a large LED A/F readout. I can then put the bike under a specific load(25%to35% usually)and isolate the different carb circuits by throttle position and rpm. An overly rich dip is pretty common on the a/f curve at the start of the run as this is when the accelerator pump is working.

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Thanks for the reply,it was at WOT and not at the beginning of the run, it was strange that it went rich and then back to a "normal" A/F reading. I was able to shift it some and help it with some filter and airbox work. Have you run any of the 250's on your dyno? It would be nice to see how the two dynos corralate. Can't give you the exact rpms right now as the dyno data is still in the truck and my boys left for Red Budd. Thanks again.

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It's the pipe...if it was EFI, we could dial it in. I will see if I can get Bryan Smith to bring his CRF250DTXer in to put on the pump...dont know anyone local that has a YZF.

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