A forum for owners of Yamaha TTR250 trail and enduro bikes!

TTRfan · Super Guru

Decompressor kit

KNjonjo · Veteran Member

Hi Brian,

I have a decompressor fitted although I don't have the cable or leve. I think the part you're asking about is the stay for the cable that mounts onto the cylinder head. Arrowed red in the attached images. Please excuse the cleanliness of my bike.

Regards

Kimani

TT-R250M · Super Guru

KNjonjo wrote:
Hi Brian,
I have a decompressor fitted although I don't have the cable or leve. I think the part you're asking about is the stay for the cable that mounts onto the cylinder head. Arrowed red in the attached images. Please excuse the cleanliness of my bike.
Regards
Kimani

Nice try Kimani but that is this piece...

Decompressor new.jpg

I think it is for the lever or cable as there is nothing like that at the motor.

Jarrah

KNjonjo · Veteran Member

You're right Jarrah. I'm 90% sure it is used to route the cable but I have no idea where it is attached.

TT-R250M · Super Guru

Yeah, I think I am closest so far KNjonjo. Somebody could still steal the prize (a pat on the back from Brian). biggrin

In case you are wondering Brian- it does seem to be a complete kit. All parts for the engine are there, the lever, and that bracket thingy that does not seem to be important.

Jarrah

TTRfan · Super Guru

TT-R250M wrote:
Yeah, I think I am closest so far KNjonjo. Somebody could still steal the prize (a pat on the back from Brian).

biggrin biggrin biggrin

I tried Fowlers of Bristol (main Yamaha dealer) and they couldn't find the kit. There must be a fiche of optional extras somewhere - one day one of us will find that fiche wink

Jarrah is right in that the mystery part was in a seperate pack with the handlebar lever so gotta be at that end I reckon but just can't figure it disbelief

Brian

TWR250funbike · Member

TT-R250M wrote:
Yeah, I think I am closest so far KNjonjo. Somebody could still steal the prize (a pat on the back from Brian).
In case you are wondering Brian- it does seem to be a complete kit. All parts for the engine are there, the lever, and that bracket thingy that does not seem to be important.
Jarrah

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Could it be true? You folks haven't cracked this mystery part in a decade?

Well, here's the possible answer if it hasn't already been offered in a newer thread.

The decompression parts from the 4gy-W0795 kit are probably only listed in a JDM fiche...maybe(as in I've never seen such such a fiche, but I know a drawing at least exists).

A complete kit comes with a drawing, complete kits are NLA.

The illustration with parts list is in "Japanese only". Not only that, but not every part in the 40 piece kit (that's right, 40 as it even includes a new clutch tab washer, and hence the reason these kits were well over $400US when they were still available).

So, while not every part is identified, the part that is the subject of this very old thread, is identifiable.

THAT PART IS 1KH-26257-00.

If I'm not mistaken, that's from a TT225 or Serow, not to be confused with the TTR225.

Anyways, that part goes on the decomp handlebar lever and it's a cable keeper meant to prevent the cable detaching from the lever at inopportune moments. The large hole points to the meter direction on the outside of the cable ferrule, and the small end points to the end of the handlebars out to infinity but forks down in between decomp lever and the perch.

As for the decomp lever and associated parts, including the cable and decomp cam. There are no part numbers, which leads me to believe it's another KIT. Or kit within a kit.....

HOWEVER THE OIL SEAL INTO THE HEAD CASTING IS LISTED, and that part is 93201-08309. Hope this helps anyone with a seeping cam arm.

PS: I see no reason why manually activated decomp wouldn't aid E-starting if needed.. It may not be just for kicks...

-- Edited by TWR250funbike on Monday 17th of July 2023 10:52:54 PM

TTRfan · Super Guru

An excellent bit of research there Michael and welcome to the forum biggrin

Brian

dlee22 · Senior Member

I've been looking for information on this for years, thanks.

I'll try refitting mine :)

TWR250funbike · Member

The kit is actually at least 43 pieces, as three part numbers are x2 pieces...it also comes with a side cover gasket.

No parts are packaged with part numbers, but they are listed on a sheet. Only 11 total parts retail below $7 US at this point(2023).

And the 43 would be a $1000 or close to it, not including an awful lot of pain and work tracking down the new and used(NLA) bits needed for a complete retrofit.

The mystery part is called a "stopper" by mister Yamaha.

TWR250funbike · Member

dlee22 wrote:
I've been looking for information on this for years, thanks.

I'll try refitting mine :)

Thanks, The one thing still a mystery (to me) is the decomp cam...At least from image searches,It seems unique to the TTR250, and I have no part number. Was there another JDM model (street maybe) with a different prefix that fits used the TTR250 engine configuration? I already know the rest of the part number would be -12288-00 or possibly an alternate suffix...the 4GY prefix doesn't work for this part, which indicates it first became avaliable for a different (probably JDM only) model.

I think the whole kicker kit was a GYTR deal originally, which explains the lack of support for the ability of tracking down the minutiae.

PS: The kit adds 1765 grams(62oz.) Or just under 4lbs.... not including the subtraction of seals, spacers, plugs etc..., removed.

-- Edited by TWR250funbike on Tuesday 18th of July 2023 07:14:58 PM