Bronze valve guide liner for small frame

[Carlos]

Has anyone tried the bronze valve guide liners?

If so, what size reamer did you use? ... i.e. What clearance do you run to the valve stem?

I'm not referring to the 9/32" hand reamer and 1/32" oversize valve that's almost impossible to keep straight, I have a pair of 1/4" bronze valve guide liners, I'd like to install one in the exhaust valve guide in an HSSK50.

I want to make sure the exhaust valve has enough clearance to take the punishment from the fixed advance solid state ignition set up, but not run Tecumseh's banana in a bucket valve to guide clearance if you get my drift!

 

[ATKRIDER]

If you can't keep the reamer straight for the OS valve how do you intend on keeping some other reamer straight?? How are you going to keep them in there after the fact? I think the "Banana in a bucket" is due to the 29313C banana-not the bucket. IF you can find a pre 1983 valve it will fit MUCH tighter. I have found that some of the aftermarket current production bananas also eliminate the wobble. I have about 10 NOS 29313c's that I can't/won't use just because of this exact problem-

 

[Carlos]

This isn't for my minibike, it's for a souped up snow thrower, I'm not looking to run a tighter valve clearance in the cast iron guide, for reasons stated below. The bronze liners I have are a perfect fit as is, but will close slightly with an interference fit in the guide, I also won't be hand reaming this sleeve.

There's a good reason for choosing the bronze liner or even a custom fit bronze guide for this issue on a tuned up snow thrower with solid state ignition.

 

[ATKRIDER]

Yea the liner is a great idea. I am going to go out on a limb here and guess that Ms. Guides have already been introduced to Mr. Reamer?
Anyway on the points engine I believe the clearance is .003". I still think keeping them in there is going to be key. Maybe groove them and use some snap ring or e-clip?? Just a thought-

 

[Carlos]

The liners are as purchased and feel perfect on the thin stem 29313C ... not reamed yet.

I've pondered how to keep them in place, especially with the heat that exhaust valve is going to be subjected to.

A liner doesn't normally need to be clipped or broached in a guide (at 0.001" to 0.0015" fit) ... but here's the kicker ... only exception SOME iron guides!

I think a minimum of 0.0015" fit (liner to guide) will keep it in place, but ONLY if I get the valve to liner clearance right! Otherwise all the high rpm, unloaded throttle conditions a snow thrower encounters and it will seize and rip that baby out of the guide!

Liner to valve I'm thinking honing to size once fiited instead of reaming ... overkill? ... Maybe, but so's the snow thrower I'm building!:drinkup:

Do you know if this .003" clearance is for pre or post '83?
Is that the tighter fit of the big banana ... or the sloppy nutty banana mix?

It appears logical that Tecumseh's solid state ignition influenced their decision to sign up for the cheapo "Back street, banana girth reduction operation." ... I'm guessing they just standardized it to include the smaller volume production engines(?)

 

[ATKRIDER]

Personally I wouldn't run them TOO tight on the stem. I usually just gauge the guide with the tapered pilot for my Neway seat cutter. If it bottoms the guide is too loose. The reason the post 83 engines run the loose guide is YES heat but it's not all due to the electronic ignition. The electronic ignition is in bed with a VERY lean carburetor and that marriage is what causes all of the heat-All small engine manufactures had to start meeting emissions standards. Once you do all of these mods you WILL have to dump more fuel into the mix and that alone will cool things down eliminating the need for the stupid loose stem to guide clearance.

As far as fitting those guides once pressed in I think a reamer is the only option. What is the OD of those liners-.315" ??

 

[Carlos]

Oh I agree that clearance to the valve can not be too tight, the whole purpose is getting it just right with this bronze liner.

I have the carb with the adjustable mixture screw on the bottom. Also 2 different jets (small hole and large hole in side) to play with, so I should have enough to richen the mixture up and "wet" that exhaust stem.

A bit more overlap from a longer duration cam would be nice for a little extra "wetting" of the ex. stem, but I've already modified the end of the cam for a Sportster rev counter and I want to see how that performs first.

Each liner has 2 bands at .317" and 2 bands that step down to .313"

Looks like post '83 the valve stem specified dia is .244"
An extra 0.005" to 0.006" clearance from pre '83?
That would make it in the region of 0.007" to 0.009" total ... that is one nutty banana!

Can you do me a favor and measure a couple of your pre '83 stems for me?
(same as inlet? ... 0.249" 0.250" ?)

As for guide sizes I can only find specs for the 9/32" oversize, which indicate 0.003" to 0.006" clearance to stem ... again nutty!

On any other engine I would like 0.0018" to .0.002" max for exhaust.
0.003" still sounds large to me on a 0.244" stem, but maybe that little extra is on the safe side.

Where did you find that figure of 0.003"?

 

[ATKRIDER]

Where did you find that figure of 0.003"?

Years of experience.

Measure your intake valve. It will be .2475-.2480". Which is dead on as SHOULD the exhaust valve be until they changed them so now they are just a pain in the Azz.

Also as I said my seat pilot is the perfect "Go-No Go" gauge which I believe to have .003" of taper. If it moves I CANNOT cut the seats. I have been using the same seat cutter for going on 17 years now but it relies 100% on the guide. ANYTHING you do to the guides is going to require that you recut the seats just to be sure. 1 degree off might as well be a mile-

Personally I use the OS stem valves. For one they ARE within the .003" clearance on BOTH and second the larger stem handles any abuse better than the smaller diameter stem-

The hardest part is boring the upper spring cap for the bigger stem.

 

[MiniDan99]

I found this post searching for ideas on how to fix my own engine (Tecumish HSSK50-67394s).

I have a low-time show blower that has a bad exhaust guide - around .025" side to side movement.
I'm thinking about reaming the steel guide oversized (or removing it all together) and pressing in a solid bronze rod, and drill/ream to size for a stock exhaust valve (#36471).

What do you guys think of this plan ? Let me know !