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

Rger8 · Member

New FMF Quiet Core 4 Exhaust installed

petenz · Super Guru

And NOT a pic in sight... cry

Maniot · Veteran Member

The securing band that comes with the FMF really needs elongated holes to help with lining up the provided bolt though the spacer......I passed this comment onto the manufacturer. Just ensure you do a plug chop ASAP as despite having a very free-flow filter fitted at the same time mine was running on the lean side.....

Terrence R · Senior Member

I just got my FMF PC4. It too has the same mounting setup. I'm waiting until I get a few Kms on in the spring. Then, I'll put the PC4, 6sigma jet kit, and Twin Air air filter all on at the same time. That way, I will really be able to feel the difference. I'll still have adjust the air/fuel screw and possible adjust the needle. But other than that, it should be pretty handy.

You should probably look into jetting and/or lifting your needle. A pipe and high flow air filter will make any bike run lean in most cases. Especially the US model TTR.

Rger8 · Member

Maniot & Terrence

Thanks for your input on bike running lean. I was going to check the plug out to see if it's looking kinda white rather than a light brown color. Not sure that's very effective but the only way I can tell it's maybe running lean. Is the easiest way to rich it up is by just backing out the air/screw mix? Maybe 2 -1/2 turns back out?

Manoit, what do you mean by a "Plug Chop" ? Thanks for passing the band install on to the Mfg.

Thanks rger8

-- Edited by Rger8 on Monday 17th of March 2014 02:59:36 PM

Maniot · Veteran Member

Rger8....Plug Chop......just a term (UK as far as I know) to describe taking the plug out, examining it and perhaps making carb adjustments or 'chopping' it in/changing it for a different grade.

Terrence R......yep, have larger jets ready to fit and intend raising needle a notch......

TTRfan · Super Guru

A plug chop simply means looking at the spark plug to determine how you are jetted at a particular throttle stage. The only tricky part is in isolating the throttle stage. Before starting, clean your spark plug and filter and warm the bike up.

To check the main jet, which operates from about 1/3 to full throttle, get the TTR up to a steady full throttle or near to it for a good few seconds, then simultaneously pull in the clutch and kill the engine. Don't let the motor drag you to a stop, or fall to an idle, because you want to isolate the plug colour at full throttle.

Get off and check the spark plug colour. It should be a light chocolate color. If it's white, the air/fuel mixture is too lean and you need a bigger main jet or raise the needle. If it's black or really dark brown, the air/fuel mixture is too rich and a smaller main jet is needed or drop the needle. If you need to change jets, change by one size, and do another run.

Fladdem · Senior Member

Thanks Brian, I needed to know that as well.

I wish I'd bought the q4, in the end it would have worked out the same price, I think. My mate has one on his CRF250L, it sounds nice and meaty, without being obnoxious, I think. I think re-jetting may help, but if the airbox is standard, then you may have leaned it out to the correct jetting. I've heard that TTR's are slightly rich from factory, although cannot confirm this.

I just got a DG-O pipe from 'Murica-land, I love it, but with my airbox having been molested by a previous owner, someone cut a great big hole in it, which I fitted a tight mesh to with rivets, better than a hole?! The bike is definitely too lean now, it pops on deceleration, like pop-pop-pop-pop, not a big backfire, it seems to have completely perfected the lag at the bottom though, mine used to bog from idle, but now it is stronger then goes back to normal. Hard to describe, no power increase except for the first quarter. Going to need re-jetting before I go anywhere again really.

Sorry for hi-jacking, here's a link to my pipe.

www.youtube.com/watch

When I turn around, google maps seems to suggest that I am about 475ft away,not really sure how far it is, but you can still hear tick-over quite well.

Now in return, I demand a clip of the Q4 doing a similar thing. ;)

Rger8 · Member

Great, and thanks to all. I'll check out the "Plug Chop" procedure and see what I get as far as running lean. It seems ok right now, no backfire at all and runs great from the bottom up to at least 65mph. I'll let you all know what I find. Great Forum!!

biggrin Rger8

Rger8 · Member

FYI,

Pulled the plug cleaned it and took it for a high speed run making sure I opened it up all the way after a good warm up. Took a look at the plug and it's a nice medium tan/brownish color. The bike ran perfect and doesn't seem to show any signs of running lean. I wonder if the FMF Q4 is a bit more like the stock pipe, that is being a bit more restrictive than the "PowerCore" therefore maybe not as critical with the jetting issues. In any case I'm happy and seems to have a nice overall increase in torque. Even a greater trail bike now!! biggrin

-- Edited by Rger8 on Saturday 22nd of March 2014 02:13:19 AM

ttboof · Super Guru

Sounds like it's pretty good . The ttr isn't a highly tuned beast so jetting isnt a perfect science ..

TT-R250M · Super Guru

The easiest way to see if you are running lean is to move the jet needle clip position two settings lower (towards the sharp end). If it starts to splutter from 3/4 throttle and pops in the exhaust a little when the throttle is let off quickly, you know it is right where it was. You should then move the clip position back to where it was.

If you find that moving the jet needle clip position does nothing or increases performance, it suggests that you are running lean. When running right, if you move it 2~3 settings lower it should start to cause a rich condition.

The Powercore is a fair bit less restrictive than the Q4 but whether or not that is better is up to anyone. IMO- the Powercore would loose too much back-pressure and reduce performance and make it run rough. It would be good to do some testing to know for sure though.

Jarrah

PlumasDude · Senior Member

Good info, thanks. I have the same year US, all stock, and I'm running a little lean at idle, current conclusion is the prior owned stored it without draining the carb so I need to suck it up and pull the carb. If it in fact has the 50 pilot jet I'm thinking of switching to the 52 after testing the clean carb, but the 52 sounds better for higher elevations. No troubles at higher rpms, but uncorking and a new pipe would be next to see about adding some kick.

TT-R250M · Super Guru

I do not see how the #52 pilot jet would be better for higher elevations as the higher you go, the smaller the jets need to be. Higher elevation= less air and the result is less fuel.

For removing the carb, see here- http://www.ttr250.com/Removing_carb/TTR_carb_removal.htm

To check and rebuild it, see here- http://ttr250.activeboard.com/t55374798/rebuilding-a-ttr250-teikei-y30p-carburettor/

It would pay to check that the accelerator nozzle is not blocked, more info here- http://ttr250.activeboard.com/t56226503/mid-rpm-range-bogs-down/

Jarrah

PlumasDude · Senior Member

Right, got that backward, thanks man. interesting tip on the accelerator nozzle. but my only problem is at idle speed, it doesn't bog noticeably with any throttle except just barely coming off idle. The pilot "wheel" or screw doesn't seem to have any real effect which makes wonder about a clogged pilot jet. It also pops just a bit while engine braking at mid range rpms, your comment the other day about needle position and those pops has me thinking but I don't see how that would be connected to my idle issue.

TTRfan · Super Guru

I have had some carb nightmares recently where, despite fitting brand new pilot jets, I haven't been able to get the slow running right. As you have found, in these circumstances, the air screw seems to have little or no effect. I tried three different carbs on the TTR that I just sold before I found one that worked properly

I have stripped and checked the dodgy carbs several times and really can't see what the problem is. I have an ultra sonic cleaner that I use plus a high powered air line. I am flummoxed....

Brian

PlumasDude · Senior Member

Well Brian if you're flummoxed then I'm probably just fecked but I'll give it a shot anyway. Funny thing is I didn't have this little issue when I bought it, it idled perfectly, I only noticed it after cleaning the air filter and pipe (which were pretty dirty when I bought it), a result that seems consistent with a gummed up carb. Maybe my son's right: "just give it more gas, idling sucks!"

ago · Veteran Member

that problem with your idle mixture sounds to me like a vacuum leak brian. it's a common cause of the idle circuit not responding to bleed screw adjustment.

ago · Veteran Member

for anybody doing an install like rqer8 did, to save yourself a lot of drama with brackets that have to be squeezed together under tension it's far simpler just to run a suitable cap screw through the frame mounting point from the " INSIDE " and then put your bracket on and either Loctite, nyloc or use two nuts to lock it on. some manufacturing engineers just don't get it i'm afraid. ever seen those car engines that use super expensive spark plugs BECAUSE you CANNOT remove them for servicing without the risk of breaking them. so they put sparkplugs in the engine that are not likely to need changing whilst under warranty. anybody tried to rotate the TTR250 gearshift on it's splines or remove the exhaust header pipe???. that's just dumb engineering logic.

Squire · Veteran Member

Rger8 wrote:
New FMF Q4 pipe yesterday on my 2003 US model TTR250

Hi, would you have the exhaust part number by any chance, I'm getting conflicting info from various retailers, thank you in advance!