Nick Novice said:
well that thread never mentions a the installation and removal on a crf. i can't get mine out w/o removing air and the chain guide. it works like a champ. but is tight.
I know but the main question to deal with here was the possible benefit with a 5" compaired to a 4.25" so I saw it relevant to the discussion.
Problems or not, if you race and don't take a second given to you for (almost) free you're a fool. I see only one other chance of getting that second, and that's loosing 5kgs either off your bike or off your belly.
I worked off a ton of weight as I started to race seriously again after a few years off coming up to this season and gained about a sec for every 5kgs lost.
Skill, physics, chassi, engine, in that order, are the most important things in SM racing. Skill and physics you get by riding, riding and riding. Nothing is as valuable as time spent on the bike. The gym has to be used with sence for a racer. Don't build where you don't need it as it makes you gain weight, where you need more strength you will feel the day after a hard day on the track. For condition run or ride bicycles.
Get a really good chassi. Suspension, wheels, brakes, see that the bike is as light as possible etc.
Then, start to work on the engine.
Mostly people go the exact other way though and as a result take 3 years more than needed to develop into fast riders. Rear wheel is a very important step, you will never win a race on a 4.25 the difference is that big.