Eric/Rich ? on Big Bore 2fiddys

Zoomer

LIFETIME SPONSOR
Nov 17, 2000
835
0
Ok,
Im thinking of going 250/big bore.
Whats out there for each, KTM , Yamaha, Honda.
Size, durability, and ease of install (machining etc)

Not really color obligated,(although I cant get a deal on a KX and don't want a Suzzy) so more looking for the best end package with the other three.

What sizes are available for each?

Do all need cases machined?

Once running with the B/B which engine would have the best reliability. I know this is more determined by the rider and how he turns the throttle and maintains the engine, but your opinion are highly regarded here.

Thanks In advance!!
Oh yea merry christmas to. :cool:
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
Mike - Two stroke or four-stroke?
 

oldguy

Always Broken
Dec 26, 1999
9,419
0
Rich he is definately going 4 stroke from when I talked to him. He had ridden a YZ250F and it reminded him how much fun the smaller (then a 450) was to ride. Keep in mind also he is planning to make a shot at Lorettas in the really old guy class this summer. We all know he twists the throttle pretty hard for a man of his advanced age
 

Zoomer

LIFETIME SPONSOR
Nov 17, 2000
835
0
oldguy said:
for a man of his advanced age

OG I havent had a Bday in 15 years, Im not that old...oldguy :nener:
Yea Rich, 4, I forgot they still make 2's :laugh:
Eric was telling me about Smulders 290, and I talked with Ed this afternoon, Totally impressed, Ed, and me.
Then he started talking about if he did it again tomorrow he would do it on a KTM or Yamaha, he had just rode them both in stock form this last weekend. go figure.
I was allset on getting a crf450, then 250, then the yamaha 250, now the ktm could be a choice. HELP! :bang:
 

Chili

Lifetime Sponsor - Photog Moderator
Apr 9, 2002
8,062
15
After watching one after another of the KTM 250SXF's go down repeatedly this past season up here I can't imagine running one stock never mind modified.
 

Zoomer

LIFETIME SPONSOR
Nov 17, 2000
835
0
Really,...I thought the sx250f was a pretty solid engine. Have not heard of any blowing up down here,
 

Chili

Lifetime Sponsor - Photog Moderator
Apr 9, 2002
8,062
15
Our top pro races one as do a few of our top C/B riders. Several of them had gearbox failures and other engine related failures. Some of them I don't know the exact details of the failure just that the kids were borrowing bikes to avoid losing points by not racing a weekend. I do know the details of 3 different ones that suffered gear box failures.
 

Eric Gorr

Engine Builder
Jun 29, 1999
384
12
Last month I became a Vertex distributor and they have a new line of big bore 4-strokes that are so big you need to modify the cases for the extra thick sleeves. I've done several CRF290s so far and now they have their KTM line up which includes a 310 and 350, thats based on the 250F which already has a head and cam made to rev. These pistons are heavier of course and thats going to reduce the longevity on the crank, but then again you're not going to have to rev it so hard to get the torque.
I ordered a 310 for Jeremy Wilkey to try on his 07 KTM250F
On the Hondas we use the #2 Hot Cam (mid to top end) and it seems to pull as long as a stocker its just strong coming out of the turns. Ed Smulders, a District 16 Vet rider consistently pulls the holeshot on 450s, even in long starts like Aztalan. Ed has 60 hours on his CRF290 now and we're taking it apart for a new cylinder head change and I'll check the rings. The new head is a 2004 with the large ports and JDM fitted Xceldyne bronze seats with 1mm oversized valves. The Vertex pistons are already sized for 1mm oversized valves with larger pockets machined in the crown.
 
Top Bottom