which crf head works best with trx bottom

[mhewitt]

im gonna buy a crf 450 head from service honda and was wandering which year would work best for my 06 trx bottom, i will be buying the bare head and water neck i want to use the rest of my stuff from my trx, so which one has best porting/most interchangeable with trx stuff. heard someting bout valve cover bing narrower in the 08 model cuz of decomp but not clear on it, any help?

[DnB_racing]

from what Ive read the 02-08 heads will work, but if the price is the same I would go with the 06 just to be sure, as ive seen a few that have done this with the 06trx and 06 crf head, the exhaust valve I think you need the crf

Im not sure if there was different port work but I do know alot of people like the 02 cam, maybe they also have different porting... if you find out please let me know

[mhewitt]

I've read that 02-05 crf have a 1mm bigger ex valve than the 06-08 crf and 06-09 trx. On service honda you can't order an 02-05 head anymore it says the part number has been replaced by the 06 head part number. There's only $25 difference between 06 head and 08 head so if it is a lil better port design for the newer head I'd rather have that one, unless I have to change out the decomp n valve cover cause then its not worth it to me.

[fmfhonda250r]

02-06 crf heads have 36/31 valves and the 07/08 have the 36/30 valves. I would get a 06 head(better seats with the bigger valves)

[DnB_racing]

Originally posted by fmfhonda250r
02-06 crf heads have 36/31 valves and the 07/08 have the 36/30 valves. I would get a 06 head(better seats with the bigger valves) is there any porting difference?

[DnB_racing]

I agree with fmfhonda go with the 06 they have the larger exhaust valve but still have the improved seats for less valve wear, Im thinking the 07-08 are made with stricter emissions standards and probably flow isn't as good

06 sounds like the best option so far.. ive been reading on thumper talk and there are many posts about the different heads and valves

im not sure how much your going to spend to get the head ready, but you can get a fully assembled brand new ported crf head from BBT for around 850, Id love to see what a ported head would do!!!!

[Chino886]

I've got a CRF head, it is 02-06 due to the size of the Ex valves. It is a bare head. PM me if interested.

[eastside 400]

heres a really good site for crf info and parts, they sell a bunch of different options for heads from bare to complete...

http://www.crfsonly.com/catalog/index.php/cPath/258_280

[mhewitt]

i would be using the valves out of my trx head in the crf head so what size r the ones in my 07 trxer head? i wanna get the right crf head to be able to swap my trx stuff in it

[mhewitt]

i went to service honda to check part#'s hoping to find which crf ex valve was the same as the trx valve and this is what i found: 06 crf ex valve - 14721-meb-670 08 crf ex valve - 14721-men-a00 o7 trx ex valve - 14721-mey-670 so im thinkin maybe the 670's are alike? can anyone confirm this?

[DnB_racing]

Originally posted by mhewitt
i would be using the valves out of my trx head in the crf head so what size r the ones in my 07 trxer head? i wanna get the right crf head to be able to swap my trx stuff in it then you need an 07 head for the 36/30 the same size as the trx valves,,, fmfhonda has the sizes

[quadfmx]

there s a guy on here took s 450R I cant rem of it was an 06 er with kicker or 06 kicker and he had a recall, and was sponsored by his local honda shop pretty heavily, anyways he turned his 450R into a 3 wheeler,
Instead of building an engine he got an 06 crf dirt bike heads and he posted dynos and it was very impressive,
It had dynos against lots of major players,
he did run a 13-1 cp piston and a different cam, maybe a hotcam but i think it was an 02 crf cam

there were some mods he hd to do to mae it work but nothing major, its had me thinking of buying one since i read about it

I ask him was it the porting or what making the diff,
i rem now it was a kicker or an er stripped down cause he ran its electronics and he said that he thought the power was there

I heard back in 04-05 pro racers running crf electronics,
it was rumors but i heard it from several different sources

[yfzfelix]

Originally posted by Chino886
I've got a CRF head, it is 02-06 due to the size of the Ex valves. It is a bare head. PM me if interested. sent you a PM about a week ago, do you still have it or not ?

[mhewitt]

he doesnt have the head for sale anymore i bought it from him

[yfzfelix]

Originally posted by mhewitt
he doesnt have the head for sale anymore i bought it from him thanks, did you buy it in the last week ?

[Chino886]

Originally posted by yfzfelix
thanks, did you buy it in the last week ?

Steve, it sold on the 26th. Sorry I did not respond sooner.

[yfzfelix]

Originally posted by Chino886
Steve, it sold on the 26th. Sorry I did not respond sooner. no problem, ever since I read this thread I have been wondering if it would be worth the time and money to switch out for a CRF head, need to do some research, Steve