Problems with new 30/24 head?

[bat999]

Anyone have any problems with these heads? I have had another exhaust valve bend. Both times these motors had less than 3 hours on them. Just wondering if anyone else has had to replace exhaust valves?

[PlanetMinis.com]

[Smokeum28]

yep my buddy had to put better valve springs and grind a little bit on the piston....

[bat999]

Emailed Mike and he is taking care of the parts. Thanks Mike.

[Double0]

sure you ajusting them rite?

[bat999]

Oh yea..........

[Double0]

Oh yea..........

you didnt ajust them?

[geezer]

Whats the complete setup? Did you check piston to valve clearance with clay first? What motor, piston, cam, ect?

[firepower354]

Verify adequate guide clearance and for a lack of galling in the guide. Heat expanding the stem, in a too-snug hole, with some old smudging, is asking for another stuck valve and the piston contact that usually follows. The stock springs are pretty darn stiff

[Smokeum28]

Verify adequate guide clearance and for a lack of galling in the guide. Heat expanding the stem, in a too-snug hole, with some old smudging, is asking for another stuck valve and the piston contact that usually follows. The stock springs are pretty darn stiff

ran in to coil bind with the stock springs running TBrace cam from 25/23 head

[firepower354]

ran in to coil bind with the stock springs running TBrace cam from 25/23 head

Wonky. TB300 is spec'd for both. I've seen a few rocker to valve issues, but not the spring thing. I have one in the shop, I'll peek at closer.

[Smokeum28]

Wonky. TB300 is spec'd for both. I've seen a few rocker to valve issues, but not the spring thing. I have one in the shop, I'll peek at closer.

and i think the stock springs only had less than 20lb seat presh...

[bat999]

yep my buddy had to put better valve springs and grind a little bit on the piston....

Where did he get the springs???

[1/4 chub]

you dont need better springs.just make sure you have 35-40lbs of seat pressure

[taz69]

you dont need better springs.just make sure you have 35-40lbs of seat pressure

How??? On this particular head you cant put shims under the springs.. There funky shaped and have a lip.. The springs in THIS head and guides I have never seen anything likie them. They are very narrow around and very tall.. The outter spring could almost fit inside a inner spring from a regular head.. Its the New TB head on a 108 with TB piston and everything. I clayed it Friday and it has a TON of room.. But it has hit the piston twice and bent the exhaust valve twice.. It had like a 16th of an inch clearance when turned over by hand so its not manufacturing in that way. The valves in this head just arent getting back out of the way at a high RPM. Yes I can push the valves off the seat with my thumb kinda easily.. With that big of a valve it should have REAL springs and because of the desighn you cant use springs from other heads ie ( Kitaco, TB, or Takegawa so on) Those heads all use the same type of spring this thing is VERY different one of a kind I would say.. So if anyone knows of some springs you can drop in here let us know.. Otherwise I told Scott he is running it at his own risk the valve pockets on the piston and the clearance is a ton something is causing them valves to not get back and that is with a TB300 cam... Runs great you just cant rev it out like the old 25/23 race head. And with the bigger valves and porting its desighned to have to operate at a higher RPM to take advantage of that but you spin this head up above 10,000 its hitting something... We go to 12,000 on our minis every day.. What is needed is a V2 desighn with honda stud spaceing.. Love my V2 1/3 the cost of my Takegawa heads and with a Takegawa cam flows JUST as good...

[fatcaaat]

back to FP's comment. The guides are too tight. heat expands, the valve gets seized up a bit and the piston smacks it. Seen it happen a bunch of times on the regular 25/22 race head. Best bet is to hone out the guides.

[taz69]

The quides are VERY honed. You put the valves in and they will fall out the quides without you touching them. Now thats with the valve seats removed cause they will cause a little drag on the valve.. There is plenty room there not dragging the guides.. The springs are to weak they have less than 20lbs seat pressure I checked today.. Thats WAY weak... They had 18lbs exactly now what ????

[1/4 chub]

The quides are VERY honed. You put the valves in and they will fall out the quides without you touching them. Now thats with the valve seats removed cause they will cause a little drag on the valve.. There is plenty room there not dragging the guides.. The springs are to weak they have less than 20lbs seat pressure I checked today.. Thats WAY weak... They had 18lbs exactly now what ????

im familiar with the valve train your using.im using those exact springs and retainers in my lifan headed/z40 cammed f2 bike(yes you have to screw the inner springs onto the valve seal).this motor revs to 13k constantly.shims can easily be added under the spring base

[taz69]

Ok cool... shims out of what type of head? All the shims I have are from the bigger springed heads.. So the TB big valve head for china engines (non KLX style top end) has the same valves? Any other head besides these 2 then use these springs? Scott may wana get with ya then on those spacers cause I just dont have anything that would work. How much did you shim yours to get the right seat pressure I dont wana coil bind the things.. And yea he just got a Z40 cam for it if I remeber right but it hit with the TB300 in there both times... He JUST put the Z40 in.. It should run good then if he can get the spring thing correct cause stock it aint all good... And yea I had to screw the inner spring around the guide to keep from tearing the valve seal.. Would be easier with the bigger style springs I would think.. Thanks for the info Dave ..... OH and where can he get guides??? He is going to need them cause the valves are REAL loose in the guides. After loosing the valves twice they are a little worn. I think Mike from TB said he had some from the older heads but those wont work. There to big around on the outside I dont think the inner spring will go around a guide from the older race heads.. So he needs to find guides if Mike dont have them were next????

[geezer]

Has anyone actually confirmed more power with this head over a YX 140 head? Im willing to do some port work on either head, And Ill buy one IF it will make more power in the end. Dose it have better shaped ports? Not just looking for bigger. Is the chamber the same size?

[taz69]

This head is for a HONDA engine. A YX head wont fit.. The stud spaceing is bigger on the china engines so you have to use heads made JUST for the Honda engines....