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I am considering purchasing a phathead aftermarket head with the 02 insert which does not require race fuel. My question is this I have heard 50/ 50 to leave the stock pipe on the yam yz85 and 50% say to put FMF fatty for the low end, will the head work ok without porting and stock exhaust or do you need the combination of all of these to get good low end power????

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I am considering purchasing a phathead aftermarket head with the 02 insert which does not require race fuel. My question is this I have heard 50/ 50 to leave the stock pipe on the yam yz85 and 50% say to put FMF fatty for the low end, will the head work ok without porting and stock exhaust or do you need the combination of all of these to get good low end power????

i know the owner of phathead personally great guy.

when my son was riding a yz80 barry put the head on and did some porting as well.

we already had a bills pipe on it the bike really came alive,the only other thing we did was change the gearing a little lower.

my son was extremely happy with the bike.

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My son raced Yamaha 85s and we had Phat Head Racing do the cylinder (103cc's) and I ran the Vforce III reed cage with the PC exhaust system. It depends on how your kid rides. My son hated the FMF because it had low end grunt he rode his in the upper end of the power band where the PC exhaust system works best. If your son likes the low end then go with FMF if he revs it out go with PC. Just my .02 Good luck. I miss the 85's. :busted:

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My son raced Yamaha 85s and we had Phat Head Racing do the cylinder (103cc's) and I ran the Vforce III reed cage with the PC exhaust system. It depends on how your kid rides. My son hated the FMF because it had low end grunt he rode his in the upper end of the power band where the PC exhaust system works best. If your son likes the low end then go with FMF if he revs it out go with PC. Just my .02 Good luck. I miss the 85's. :busted:

we had better performance with bills then pc,did you ever try bills just out of curiosity?:moon:

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we had better performance with bills then pc,did you ever try bills just out of curiosity?:busted:

No. I've heard of Bills pipes. What does it do to the power band? Is it good everywhere in the power band?

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No. I've heard of Bills pipes. What does it do to the power band? Is it good everywhere in the power band?

it seemed to have a little more in the mid range and the top

the bottom end was about the same:thumbsup:

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it seemed to have a little more in the mid range and the top

the bottom end was about the same:thumbsup:

That does sound better than the PC pipe. The PC was all top end and the way my son raced 85's more in the mid would have made it even better. Do you know how they are on 4-strokes?

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That does sound better than the PC pipe. The PC was all top end and the way my son raced 85's more in the mid would have made it even better. Do you know how they are on 4-strokes?

we run them on my sons CRF450s and they are great,i race with an old timers club and have it on mine as well and am very happy with the pipe.:busted:

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we run them on my sons CRF450s and they are great,i race with an old timers club and have it on mine as well and am very happy with the pipe.:busted:

I'll have to research them. My son races a YZ250F in the intermediate/B class. Do you know what they run price wise aprox? He's in Cali practicing for the next 2 weeks and just broke the stock exhaust pipe in 2 so I will need to get another exhaust system when he gets back.

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Hey I was wondering what gearing you went to. My son had a kx 65 and that bike is the same no low end and all mid to top with a bills pipe I got really cheap from ebay. If you google yz 85 low end power you will come up with a thread from here and this guy suggested using the slide and needle from a kx 85 to get rid of the rich jetting these yams have. He said his son just went to a 125 and did the same thing. He also said the stock pipe was as good as you were going to get power wise just get a silencer to let it breath. Have you heard of any of this????

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do you have a contact number for phathead racing and I was wondering what advantage this head will have over shaving .003-.005 off the existing head and polishing it???

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the DOMA pipe is what you will want for the yz85,

hands down the best for the YZ, bills would be next on my list

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it was a while back but we went i believe 5-6 teeth bigger on the rear is where it worked best but we did experiment a bit to find what was best for him.

phatheads # is 951 371 1329 his name is barry great guy very smart

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thanks for the info I will look into the pipes and such it just drives me nuts that there is no low end power in this thing out of the corners.

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