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

Padowan · Senior Member

Accelerator pump return spring

TTRfan · Super Guru

So I am not the only one that does that Simon!

I have a nearly new Parkside electric staple gun that I took apart to free a jammed staple (unnecessarily so apparently disbelief ) and a tiny spring flew out. It's somewhere on the bench but I can't find it and the gun won't work without it cry

Anyways up, the part number of that spring (#38 on the fiche) is 6G8-14275-00 and the retail price is a silly £6.85 bleh

I think that as long as the spring is strong enough to return the diaphragm you would be OK. I have one out of a carb here that you are welcome to borrow to match up if you want?

Brian

Padowan · Senior Member

Looking at the parts fiche, the spring, item #37 here, is also used up the top, near part #40, but I can't work out what exactly that is? Perhaps the one used by part #40 is less critical and I could swap and then replace the one at the top with a random one?

TTRfan · Super Guru

Well spotted!

Part 40 on your fiche is the accelerator pump actuating arm. However it isn't physically attached to the diaphragm rod so, whilst the rod is returned after use, the diaphragm would stay down without its own spring.

Brian

TT-R250M · Super Guru

Padowan wrote:
Looking at the parts fiche, the spring, item #37 here, is also used up the top, near part #40, but I can't work out what exactly that is? Perhaps the one used by part #40 is less critical and I could swap and then replace the one at the top with a random one?

The part that goes under part #40 is called the diaphragm lever arm spring. They are both the same and are also used in other models, see link below- http://www.boats.net/parts/detail/yamaha/Y-6G8-14275-00-00.html

The diaphragm lever arm springs job is to return the diaphragm lever arm when the throttle is let off. Without it the diaphragm would get stuck down as the diaphragm lever arm would not return as intended to. Having the correct spring rate for the diaphragm lever arm spring is nearly as important as having the correct spring rate as the diaphragm lower spring.

That said, any spring that is close enough should suffice.

Jarrah

Padowan · Senior Member

Thanks for the advice! I've found a spring that fits from inside an old car cigarette lighter plug, and I chopped it down so that the pressure required to press the diaphragm felt "about right", although that's very subjective as I couldn't really remember how firm it was before hand.

Anyhow, the bike's starting, idling and running OK and picks up when the throttle opens. On a perhaps unrelated side note, it seems to be occasionally mis-firing so I might change the plug to rule that out.

TT-R250M · Super Guru

Padowan wrote:
On a perhaps unrelated side note, it seems to be occasionally mis-firing so I might change the plug to rule that out.

When does it misfire?- on hard acceleration, mid throttle?

Padowan · Senior Member

Just randomly. Will sit there purring OK on idle, then it'll miss a beat and then carry on (although sometimes it'll miss and then cut out when idling).

I've not changed any of the jetting, and have set the mixture screw to 2 turns out but I'm wondering if there's also some other fueling tweak needed as it's backfiring on overrun which I believe indicates lean runnning.

TT-R250M · Super Guru

Padowan wrote:
Just randomly. Will sit there purring OK on idle, then it'll miss a beat and then carry on (although sometimes it'll miss and then cut out when idling).

I've not changed any of the jetting, and have set the mixture screw to 2 turns out but I'm wondering if there's also some other fueling tweak needed as it's backfiring on overrun which I believe indicates lean running.

Do you mean that it backfires when you accelerate or decelerate and at what rev range?

Does it have any other problems worth mentioning?

Padowan · Senior Member

Just blipping the throttle in the garage, haven't take it out for a ride yet. Backfires are on overrun, when you shut the throttle.

No other problems, this one's really tidy, but doesn't get used much.