YZ250F do I big bore or don't bother

Ok the bike (2006) already has a header, pipe, high comp piston, jet kit jetted for 50/50 mix race gas with pump, ported and polished head, stock cams, I obsolutely love the bike and don't want to upgrade to the newer 250f because I dont think its worth the money seeing how I dont have any problems with the new 250's on the track.

Now here is my dilemma I race 2 vet classes 25C and Open C and after this spring half I will be moving up to B, if I get a top 10 start I always finish top 3 bearing some crash offcourse but on ceratin tracks with long straights or sand starts I can't get good starts and 4to 5 laps never gives me enough time to get back to the front and ill crack the top 6 usually.

I'm 6.1 and 185 lbs, is the 290 kit worth the bang for the buck or should I just throw in the towel and get a 450 like people have been telling me. I've been on 250F''s since they came out from yamaha and have grown so used to the bikes thats its hard to give up the light weight and rev happy riding.

Sorry to be so long winded but guys with 290 kits, are they reliable, how long before rebuilds, is the power worth it.

Thanks in advance.

I've had an Athena 290 kit on my bike for a whole season, and I just took it down for inspection. The bore, piston coating, and rings are all nearly as good as new, and going back as they are. I could have not bothered, but I wanted to check the crank too, which is good to go for another year also.

I think a big-bore is a better value than a trick pipe; I have a stock pipe, stock cams, and close-to-stock jetting in mine, and it rips!

I've had an Athena 290 kit on my bike for a whole season, and I just took it down for inspection. The bore, piston coating, and rings are all nearly as good as new, and going back as they are. I could have not bothered, but I wanted to check the crank too, which is good to go for another year also.

I think a big-bore is a better value than a trick pipe; I have a stock pipe, stock cams, and close-to-stock jetting in mine, and it rips!

What did your wrist pin look like? I'm asking because I tore my bike down after a year of riding to install a BB kit and the piston and cylinder look good, but the chrome on the wrist pin had come off where it rides in the connecting rod. The rod small end is still in spec but there was enough of a ridge on the pin to feel with my finger nail. Just wondering if this is common or not, don't hear to many people comment on the wrist pin's condition. I didn't have the total hours on the bike, but I bought in new in Dec 08, and it has 2000 miles of trail riding and Hare Scrambles on it. If this is common it would join the cam chain as a weak point on these engines, I know it is something I'll look for from now on.

When did you install the big bore kit? I want to install one in mine but have questions on weather the stock crank(never replaced) could handle it? Ive been advised to replace the crank before doing so

If the stock crank is in spec it should be fine, I'm still waiting on my kit to get here. I've received my cams, cam chain, front rim, hot cams shim kit, hour meter, tools, but I'm waiting on my ASI radiators, BB kit, and Smart Performance WRF Phase 4 kit.

When did you install the big bore kit? I want to install one in mine but have questions on weather the stock crank(never replaced) could handle it? Ive been advised to replace the crank before doing so

i have an athena on my 04 wr with 180 hours on it going strong. i change the piston on it every 50 hours.i put the kit on when the motor had 30 hours on it.

Which athena kit do you have and is it on the stock crank? Do you actually have an hr meter or are you estimating?

If you go with the JE 290 kit you get everything you would with the Athena kit for $387.00 vs $500+. You can then take the money you saved and buy some aftermarket cams! Eddie, resident jetting and engine expert on TT, said the Athena's are over priced because they used to be the only company that came with an aftermarket cylinder. This is no longer the case, but they didn't lower their prices to be competitive.

Which athena kit do you have and is it on the stock crank? Do you actually have an hr meter or are you estimating?

i have a 290 kit and yes i have an hour meter on it. i just sold the 290 kit and put an stock 07 wr top end on it.head cylinder and piston, the motor is still running strong. i don't beat my bike but i do ride them fast the motor has never seen the rev limter but it up high in rev alot. i had a reklus in the hole time the big bore kit was in it and an oil cooler on it.i put a timing chain in it when i did the third piston. there is a total of a 213.8 hours on the bottom end i bought it with 30 hours on it.the hour meter was put on when new. i changed the oil after ever ride. 5-6 hours of riding time.oil filter ever third oil change. air filter cleaned after every ride.

i have a 290 kit and yes i have an hour meter on it. i just sold the 290 kit and put an stock 07 wr top end on it.head cylinder and piston, the motor is still running strong.

Landshark,

Why would you go back to a stock piston? Was the 2007 motor better than the 290 setup?

Wich bb kit is the one to buy?

Wiseco

JE

Magnum (with je piston)

Or the athena

now there is a BIG question, everyone has a differing opinion on this subject

i have recently fitted the Athena and have found no problems

just great pleasure from the extra power.

The Wiseco is the new kid on the block with some funky coatings, but all of them are proven reliable. The Athena is more expensive, the gaskets are stupid expensive for a gasket, and it says "Athena" on the side of the cylinder, and if your trying to keep it low profile, nothing screams "IM CHEATING" like an Athena cylinder.

Landshark,

Why would you go back to a stock piston? Was the 2007 motor better than the 290 setup?

just to sell it. i had the o7 piston and cyclinder from an 07 wr i put a 290 kit in new. the 04 wr motor needed a head i found a used 07 wr head and built the motor with it and sold the 290 kit now tring to sell the motor. no the the 07 motor is not better stock over one that has a 290 kit in it.my 07 wr motor has a 290 kit in it stage 2 exhaust stage 1 intake with a reklus auto clutch stock 06 header pipe Q4 muffler with an 08 yz carb on it. the motor is in an 07 yz250f. i race dist 36 enduro on it.

Wich bb kit is the one to buy?

Wiseco

JE

Magnum (with je piston)

Or the athena

I would say which ever you get for a better price, they all have good reliability as long as they are installed right. The Magnum one and the JE are the exact same thing, I believe cylinder works makes the cylinders for JE and just re-badges the kit for Magnum. So go with it since it is only $375 and use the money you save over the Athena kit to buy some cams! You will like the BB kit way more if you include more lift and duration aftermarket cams.

I would say which ever you get for a better price, they all have good reliability as long as they are installed right. The Magnum one and the JE are the exact same thing, I believe cylinder works makes the cylinders for JE and just re-badges the kit for Magnum. So go with it since it is only $375 and use the money you save over the Athena kit to buy some cams! You will like the BB kit way more if you include more lift and duration aftermarket cams.

That sound great, i do now have stage 1 HC in both intake and exhaust.

I read somewhere that changing one of them to a stage 2 would be better,??

The stage 1 intake with the stage 2 exhaust is supposed to add as much on bottom as both stage 1's, but with more on top. As long as you have aftermarket cams already though you'll be fine. There is a dyno with a 290 and both stage 1's in it and it added more power everywhere, even on top.

Found a used athena kit (around 15h on it and cheap) here in Sweden.(a new one is around $1000 here with current exchange rate)

Im gona use new gaskets but read somwhere that its god to put some coppergrease or something on the gasket before mounting for longer/safer gasket life.

I`m i wrong ? what is the best way of mounting it?

MVH Henric

Found a used athena kit (around 15h on it and cheap) here in Sweden.(a new one is around $1000 here with current exchange rate)

Im gona use new gaskets but read somwhere that its god to put some coppergrease or something on the gasket before mounting for longer/safer gasket life.

I`m i wrong ? what is the best way of mounting it?

MVH Henric

i have changed the piston in mine three times and have had no problems just runnig the gasket as they come putting nothing on them at all. i change te piston ever 40-50 hours and i races dist 36 enduros with it

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