yz465h. no torque like i remember!

[oldfart]

Has anyone mentioned crank seals... worth a thought .

[lms6201]

Has anyone mentioned crank seals... worth a thought .

a second thought , thanks old fart  , even though i,d replaced them on mine , i checked them , and found one had worked it,s way out some how , evo at dundowran park hearvy bay tomorrow, still not quite rite jetted but good enough to ride   

[E74]

sounds like an air leak to me, check your base gasket and for cracks in the cases near the base gasket.

do this BEFORE anything else!, I have lived and breathed  these things for way too long and that is where I would go first.

[YZ250H]

Success - Installed the new reeds and we are back in Business.  When I pulled the reed case out one of the reed screws was sitting loose on the intake.  I think it was trapped there by the reed cage, but would have been disasterous if it had escaped.  I have gone back to standard jetting apart from the 400 main ('cause the 390 hasn't arrived yet).  I fiddle with it a bit as response of the bottom is a little flat.  Pilot screw is out 1 and 3 quarter turns -I'll have a play with that.
So don't know if the reeds were fatigued or wether that loose screw had something to with it.
Now I just have to find a long enough straight to do a few chop tests - Can this be done in say third ??.  Full throttle in top is getting pretty quick.

[evo550]

Can this be done in say third ??.  Full throttle in top is getting pretty quick.

Pussy

[lms6201]

 good to see u have had some success , mine ran well for a further 10 seconds ,, how hard is it to bend a crank , or how easily are they to get mis alined ? sucked in the base gasket again , what is good for case sealant ? i,m going to re kit the engine and start again 

[DJRacing]

good to see u have had some success , mine ran well for a further 10 seconds ,, how hard is it to bend a crank , or how easily are they to get mis alined ? sucked in the base gasket again , what is good for case sealant ? i,m going to re kit the engine and start again 

Have a think about getting the cases machined matched with the barrel so that the base gasket has even pressure on it when torqued down. Check the studs in the cases for pulling out or stretched threads. Do a pressure test once you have the motor back together and if all is ok then you have a good place to start working through any other problems.

[jimg1au]

plug chops
full noise in 3rd is ok to do a plug chop.
cheers
jim

[YZ250H]

Good on you  Jim.  3rd will make the whole thing slightly more civilised.  Full noise in top is fairly moving and the last thing on my mind would be the chop test .  Self preservation would be most important I think.

Bad luck lms  :'( :'(.  Any idea what the cause was ?  Hope she comes back bigger and better.  Threebond grey is the best sealant by all accounts.

[lms6201]

 me too , strip it down and start again , i did run it for one race ,  but barley controlable as it went from absolute blubbery to holeshot weapon when it got extra air intake boost  , wonder if i can patent that ?  will have to find the vibration as well , if that doesn,t work , i,ll drop a 490 in it

[torm92]

With the base gaskets being sucked in , i have "yamabonded' mine on the transfer port edges . The experts told me not too , but ever since I have done this , no issues. You must remember that it is a big compressor /piston moving a lot of air around , especially when dirt tracking.And a 465/490 is a great dirt track bike , set up right will outrun a 450 modern.

[holeshot buddy]

make your own base gaskets
make them about 2.0mm wider
around transfer edges
you can also centre punch small holes on both surfaces

[lms6201]

rusty does the center popping apply to the crankcase ? does it help to hold the base gasket in place ? have been cutting my own gasket,s for ages , out of all the yams this one is the only one i,ve had problems with , and  i,ve used miss matched cases ect , seem,s more care i put in , more problems, experienced !   must be some warping , torm 92 , i have used sealant on the base before , and it let go in no time , could be the vibration i,m trying to find , anyone got a good crank ? cheap 

[holeshot buddy]

yeah you centre pop both surfaces
and cut your gasket like i said
and match up all inside edges
you can put non hardening permatex
on both sides of gasket i have
had a lot of success with it

[lms6201]

yip yip , it now has torque (and everyingthing else) plus a bit more like it did a long time ago , hope it lasts , i suspect the sealant i first used on the crankcase halves started to fail , thanks everybody for the 3 bond advise , for the vibration problem , i made a set of heavier frount mounts and fitted a head stay ,i did have the crank professionally checked , it was within .003"  but they got it to .001" well worth the $47 for peace of mind ,when i first assembled the engine the origional bearings seemed ok but were now a little loose , so new ones fitted, may have helped ,another set of new seals too ,    i fitted a 490j manifold and yeis can , , makes it a little more forgiving to jet , as for the base gasket problem , i bought a new wr one , they have a line of raised rubberey stuff on them , to help stop slippage i feel ,and a little 3 bond on the other side , genuine parts cost lots ,$33 ,  torwards the end of the session it did start to play up down low , on checking it would have had less than a litre of fuel in it when this happened so i think low fuel pressure , the cylinder has had extensive porting and is very smooth in the transfers and ex , intake looks to have been lowered , 490 dg pipe , 2mm os , big jets, 6f16 / r0,  40 pilot,  main is 440 very crisp  or 450  to richen it a bit for lots of wide open running , now all i gotta do is get it to stop !   i tried a champion n3c plug in one of the 490,s last week , first time ever started first kick , and it stopped 90% of pinging , which worries me ,