Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: Isobareng on December 19, 2010, 05:51:38 PM
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Yes,yes, yes the four strokes are easier to go fast on���..
How about a little article on what I see coming through my shop these days. I would hope that after 32 years of being a mechanic a few folks might give ear to this old timer and pick up on where the 4 stroke world is in regards to keeping a motocross bike in racing condition.
Are 250Fâ??s disposable?
A Brand new, one year old, left over 250Fâ??s sitting on the dealers floor can be had for around $4K.
In the shop I see a river of 250Fâ??s that have seen very little maintenance. Crank shafts worn out, cylinder heads beyond economical repair. Repair bills that can run well into the $1500 +++ range. I see rods sticking out of engine cases some even break the bottom of the cylinder off as a bonus. Add in a worn shock body and seized up linkage bearings one can get very close to treating a 250F like a Bic lighter.
With a rev limiter set around 13000 RPM these hyperactive bikes provide a lot of thrill but at what cost. How many of the folks out there will still be in the sport with the cost of keeping one of these bikes in racing condition?
The 450Fâ??s are a bit of an improvement. The lower RPMâ??s provide longer life. But I still see very few folks keeping up with their maintenance. Rebuilds on the 450Fâ??s can be made tiny bit cheaper if the owner wants to switch to stainless valves from titanium. However some of the savings are lost as the stainless valves need better springs.
Here is a maintenance schedule for the amateur racer that is based solely on my opinion of what I see in the shop for 4 strokes. If the manufacture suggests you perform these items sooner then always go with the manufacturer.
Inspect
Fluid levels.
Hardware and spoke security,
Wheel hubs and frame for cracks,
Tire pressure,
Cable adjustment, Sprockets for serviceability
Chain lube and tension. ������������..........................Every Ride.
Air Filter
Clay based and loam tracks ������������....................Every Ride.
Sand, dusty and ash tracks.... ������������. �����Every Moto
Indoors arenacross......... ������������................Every other ride
Drain Carb ������������..............................................After each wash
Oil only change ������������.....................................2.5 Hours
Oil and Filter and oil tank screen cleaning ���������..�.5 hours
Valve Clearance check ������������..not more then 10 hours !!!
After a shim size change check again in 5 hours,
Valves������������................................................On condition
When a valve requires its second smaller shim size installed not counting break-in adjustments its time for the valves to be replaced. Springs should be replaced on
250Fs around 40 hours and 60 hours on 450Fs.
Clutch inspection ������������...........................On Condition
At the first sign of any slipping or before any important race.
Piston and Rings replaced
Cylinder and cam and crankshaft inspectionâ?¦40 hours 250F and 60 hours on a 450F
Cam Chain replaced������������.............................80 hours
Lube shock linkage, swing arm and steering headâ?¦..Pressure washing 8 rides
Hose washing 25 rides
Fork and shock oil change������������.......... Every 25 rides
How many folks actually keep up with this type of schedule? Not many, but this is what it takes to keep a 4 stroke race ready at the amateur level.
What about the 2 strokes?
Lets count the ways a 2 stroke is nicer to its owner.
1. Missing $150 EACH titanium valves, seals and spring sets.
2. Missing Crankshaft counter balancer and 2 bearings for it.
3. Missing cams, shims, and plain bearings that take a head replacement to fix.
4. Missing an Oil pump
5. Missing a Oil filter.
6. Missing Oil screens that can be clogged with clutch debris.
7. Missing a Cam chain, tensioner and guides.
8. Missing Valve guides and seats
9. Missing unpredictable bogs on the face of a jump
10. Missing a computerized Fuel injection system to get them to run right.
11. Missing $1000 exhaust systems
12. Missing $11 a quart oil.
And what it hasâ?¦.
13. A top end kit for a fresh motor $150
14. Just about anyone can do a top end .
15. New exhaust pipe for $250
16. 2 strokes peg the fun meter
17. They are lighter
18. They usually turn better.
19. They are easier to ride on sand tracks
20. A 250 usually has a rev limit around 8500 RPM so the cranks tend to last longer.
21. Its easy to distract a 4 stroke rider in front of you with the sound of a 2T
Hope you all enjoyed this article.
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That was great! :) Looking forward to more in the future!
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Great article!
It would be interesting to compare maintenance schedules/costs of a Honda CR450F vs. a CR500AF over the span of one year.Having owned a motorsports business myself and having repaired numerous 4st's I instinctively didn't fall for the 4st hype and stuck with 2 st's.Virtually every friend I have went the 4st route and is now back on a 2st.Like cigarette smoking,they can't figure out why they went down the 4st path in the first place.
I live in the snowbelt and I've heard but one 4st sled in the neighbourhood.Some of the 2st snowmobiles sound like TZ250's when they go by my place.
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Good read! Welcome to the forum! :)
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thanks
great write up!!
:D
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Great first post. And so, so true !!
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fantastic reading. i own a crf450x and come close to the maintainance schedule you mention for the most part anyway. I laugh at my mates on there 4t's when they wont start anymore on the side of a very steep hillclimb in the middle of nowhere, and they say i do to much maintainance when they never do any, but you right with the 2t's every now and again and maybe a new plug with mine every so often, not bad at all, and so much more fun to ride , the 2t