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Discussion Starter · #1 ·
Since my 450 is breaking radiators for no reason and coolant is in the oil and metal shavings are in the filter im going to re overhaul it this winter. What would some of you suggest for a good reliable trail motor that i can get 500 or more hours out of. Is this possible? Input appriciated.
 

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OEM WR crank and a 12.5 piston with oil mod will last a long time. new head bolts, clean all threads of oil and such and Cometic or OEM gaskets will be a good start.
 

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I'm sure there are a couple years that work but I always order a 04 WR crank. Never buy a YZ crank. It will not work with the flywheel and stator set ups.

I prefer CP pistons.
 

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Discussion Starter · #7 ·
I'm sure there are a couple years that work but I always order a 04 WR crank. Never buy a YZ crank. It will not work with the flywheel and stator set ups.

I prefer CP pistons.
Thanks, that sounds good and should i get like a +6 flywheel since its a trail bike, or is the weight loss of the wr crank not going to affect it? I just don't want to stall it all the time.
 

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IMO for a trail quad gearing helps stalling and slow speed driveability more then changing the fly wheel. I would just run the OEM flywheel and play with gearing. With a YFZ450 when all I did was trail ride I liked a 13 tooth front sprocket with stock size tires.
 

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Discussion Starter · #9 ·
IMO for a trail quad gearing helps stalling and slow speed driveability more then changing the fly wheel. I would just run the OEM flywheel and play with gearing. With a YFZ450 when all I did was trail ride I liked a 13 tooth front sprocket with stock size tires.
Hopefully stock gearing will be fine, i have stock gearing and like that for top end. I also have stock size tires.
 

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Discussion Starter · #10 ·
Is there an advantage to the wr crank other than the faster reving? I dont need faster revving, its a trail quad so all that will be useful for is putting it into a tree faster. If its more reliable and will last longer i will use the wr crank but out of all the cranks, the 05, 06+ and wr, is one more reliable than the other?

If i was planning to drag it all the time i would probably go with the wr crank to rev faster and get off the line faster, but all i care about with this build is reliability.
 

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Internally, I´d probably just go with an OEM 06+ YFZ crank and make sure the oil mod is done for the bottom end, and then headwork from a reputable shop and a 12.5:1 (max) piston or even an OEM piston with OEM cams. Not very daring, I know, but it should be good for a lot of hours of fun. Externally, I´d just install a good pipe (Yoshimura is my favorite all-around pipe) and then an FCI with the box and either the FCI pleated filter with a pre-filter, or a quality foam filter. That´d be my suggestion. Should be really reliable and plenty of power for a trail rig.
 

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Discussion Starter · #12 · (Edited)
Internally, I´d probably just go with an OEM 06+ YFZ crank and make sure the oil mod is done for the bottom end, and then headwork from a reputable shop and a 12.5:1 (max) piston or even an OEM piston with OEM cams. Not very daring, I know, but it should be good for a lot of hours of fun. Externally, I´d just install a good pipe (Yoshimura is my favorite all-around pipe) and then an FCI with the box and either the FCI pleated filter with a pre-filter, or a quality foam filter. That´d be my suggestion. Should be really reliable and plenty of power for a trail rig.
Thanks, and thats almost what i was thinking. For a piston i will probably sell my athena that is in it and go with a cp because i hear they are heavy. Added rotational mass to a crank (like a heavier piston) would actually good in a lot of cases like trails, it takes it longer to get up to speed but once it gets there it can keep going and thats what you need while riding trails.

For an intake, ill probably run an fci with box. I might even send the head out for porting. Exhaust, i can get a yoshimura for $400, but The reason that pipe is so cheap the muffler is made out of aluminum which melts at 1220 degrees, so if the exhaust got hot enough, the muffler could melt. They did make the header out of stainless steel though so that would be all thats left. I wish i knew the temps of the 450's exhaust.
 

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Your exhaust should never get hot enough to melt your muffler. The only time I´ve ever heard of that happening is if the machine caught fire and burned completely-- in which case the muffler would likely not be your biggest concern. Also, about rotational mass and inertia of the piston, simply changing the weight of the piston wouldn´t necessarily give you an advantage on the trail (or anywhere else) unless the crankshaft required counterbalancing and received it in the form of a heavier piston. The way to add inertia without upsetting the internal balance in your case would be to add a flywheel weight or maybe some unsprung weight in the form of heavier tires. The tires would only help you maintain momentum if you´re already in motion, and if the clutch isn´t pulled in. In your case, for momentum/inertia, I´d either leave it be or add a flywheel weight or a heavier flywheel. Just my opinion. Otherwise, I´ve heard that the Rekluse clutch assembly adds a bit of weight, which would act like a flywheel weight. You may want to look into that, as well. Good luck with your search and your build.
 

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WR rod is longer then any yfz (atv) rod given equal stroke. So the rod to stroke angle is better, TDC is taller in the bore which = more compression. Which is exactly why the wr449cc motor is 12.5 compression and the 06+ yfz 449cc motor is 11.4. Same stroke distance, same bore, but being taller in the bore at TDC = more compression.

You will not notice any rev speed trail riding, so I wouldn't worry about that.

You may notice a WR crank vibrate more. Some feel it, others do not.

IF you want the 10cc gain of the WR or 06+ crank, IMO get which ever crank you can get a piston for and for the cheapest amount. Between the 2 cranks, wr and 06+ for trail riding IMO they are pretty close to being the same. If WR pistons are harder to get... 18mm wrist pin vs. 20mm for the yfz then stay with a yfz crank. Piston choices "may" be easier to come by.

Like I mentioned earlier, gearing will play a bigger roll in trail riding then crank mass. If you get real anal over it, you could go with a heavier flywheel from trail tech. I personally have never liked Trail tech's lighter weight fly wheels, as they crap out, so I never consider swapping out a proven fly wheel like a OEM Yamaha designed unit.
 

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Discussion Starter · #15 ·
WR rod is longer then any yfz (atv) rod given equal stroke. So the rod to stroke angle is better, TDC is taller in the bore which = more compression. Which is exactly why the wr449cc motor is 12.5 compression and the 06+ yfz 449cc motor is 11.4. Same stroke distance, same bore, but being taller in the bore at TDC = more compression.

You will not notice any rev speed trail riding, so I wouldn't worry about that.

You may notice a WR crank vibrate more. Some feel it, others do not.

IF you want the 10cc gain of the WR or 06+ crank, IMO get which ever crank you can get a piston for and for the cheapest amount. Between the 2 cranks, wr and 06+ for trail riding IMO they are pretty close to being the same. If WR pistons are harder to get... 18mm wrist pin vs. 20mm for the yfz then stay with a yfz crank. Piston choices "may" be easier to come by.

Like I mentioned earlier, gearing will play a bigger roll in trail riding then crank mass. If you get real anal over it, you could go with a heavier flywheel from trail tech. I personally have never liked Trail tech's lighter weight fly wheels, as they crap out, so I never consider swapping out a proven fly wheel like a OEM Yamaha designed unit.
Thanks, and i will have to look around for a good deal for a crank and piston. A cp piston would probably be the most reliable one right? It seems everyone has a cp and they last forever. It has a hotrods crank and athena piston in it now. They still look good, but i dont trust the hotrods crank and a cp is a much better piston than athena. By the way this is a stock bore athena, not big bore. They aren't popular, but they were made.

Who makes the best cylinder? I dont really want to pay $250 for a new one, but if i have to i guess i will.
 

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Discussion Starter · #16 ·
Your exhaust should never get hot enough to melt your muffler. The only time I´ve ever heard of that happening is if the machine caught fire and burned completely-- in which case the muffler would likely not be your biggest concern. Also, about rotational mass and inertia of the piston, simply changing the weight of the piston wouldn´t necessarily give you an advantage on the trail (or anywhere else) unless the crankshaft required counterbalancing and received it in the form of a heavier piston. The way to add inertia without upsetting the internal balance in your case would be to add a flywheel weight or maybe some unsprung weight in the form of heavier tires. The tires would only help you maintain momentum if you´re already in motion, and if the clutch isn´t pulled in. In your case, for momentum/inertia, I´d either leave it be or add a flywheel weight or a heavier flywheel. Just my opinion. Otherwise, I´ve heard that the Rekluse clutch assembly adds a bit of weight, which would act like a flywheel weight. You may want to look into that, as well. Good luck with your search and your build.
Thanks for the exhaust info, and what i meant by the heavier piston was the fast it should rev a bit slower. For the flywheel l may add a weight, that seems like a good idea. I do have a rekluse clutch basket already.
 

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Thanks, and i will have to look around for a good deal for a crank and piston. A cp piston would probably be the most reliable one right? It seems everyone has a cp and they last forever. It has a hotrods crank and athena piston in it now. They still look good, but i dont trust the hotrods crank and a cp is a much better piston than athena. By the way this is a stock bore athena, not big bore. They aren't popular, but they were made.

Who makes the best cylinder? I dont really want to pay $250 for a new one, but if i have to i guess i will.
Best stock bore cylinder? Athena may be better then OEM, due to larger water jackets. JSR is best for big bore, but you will not find one in your price range. Athena would be best big bore for cost and reliability stand point.

CP IMO is the best aftermarket piston, quality, price, features, and vendor support.
 

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Discussion Starter · #18 ·
Best stock bore cylinder? Athena may be better then OEM, due to larger water jackets. JSR is best for big bore, but you will not find one in your price range. Athena would be best big bore for cost and reliability stand point.

CP IMO is the best aftermarket piston, quality, price, features, and vendor support.
Athena has larger water jackets on stock bore piston cylinders? I have an athena stock bore piston, not the 98mm big bore.

Id like to use a stock bore cp piston but i don't know what cylinder to buy. I would like to stay stock bore because it will be a true 450 and it will be more reliable than a big bore, less stress on the crank. I am just wondering if there is someone aftermarket who makes a cylinder that is as good or better than oem for stock 95mm bore.
 

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I just did a complete rebuild for a friend for a 08 yfz 450
He threw a chain and crackd his cases so we overhauled the hole thing!

Brand new oem cases
All new oem bearings
All new oem seals/gaskets
Cyclinder works cylinder kit w piston 12:1
Hot rods crank
He kept his head stock but cams mayb in the works in the future

I would recomend for your build all new bearings in the cases and oem gaskets,seals look over your cylinder and make sure it is in good shape otherwise replace you can go oem or cylinder works the complete kits are awsome been running there stuff for years with no issues and using vertex pistons id also send your head out for inspection and a valve job/deckd if needed and if on the budget a port/polish mxp would b my recomendation for head work
I have a 2010 yfz450x i did basically the same mods and shes running strong still after 12 xc races/practice rides this season alone!
 

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And for trail riding look into a rekluse for your stalling issues good investment!
Heres my buddys 2008 yfz450 build
We did a rekluse core exp in this motor also!




 
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