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

Members Login
Username 
 
Password 
    Remember Me  
Post Info TOPIC: Alternative carbs for the TTR250 - 32mm carb


Super Guru

Status: Offline
Posts: 1379
Date:
32mm carb
Permalink  
 


Very jealous of the speed at which your project is travelling! I'm still at the mercy of a foundry with batch processes - got 2 350 barrels cast but probably won't have them heat treated 'till next month 'cause they're about to go into a 2 week summer shutdown. Aaargh. I will probably try a different foundry next time...

Thanks for the cv carb info Chris, by the way. I know the pumper carb works well on my 325 over a wide range of altitude without modifying the jets. If the Koso does too, I will certainly look at it for the 350. I have a mate who's 250 was playing up on a trip we did and he was looking at a cv carb conversion. Decided to give his carb a good clean first, found the pumper jet blocked. Cleaned it and transformed the bike. Who'd have thought it

Wonder if the outside diameters of the in/outlets are larger on the bigger carbs or is it just the throat diameters.

Hope the ribs are healing,
Simon.

__________________


Senior Member

Status: Offline
Posts: 127
Date:
Permalink  
 

I bought also KOSO carb and jettings. It should come after one month or so. I let you know if I get the same results with the same jettings on my TTR 250 OE.

Today, I a bought a new old bike 1999 DR 350 with electric start. I also planning to try one of bigger cv power jet carbs.
FBRConcepts, could you share with us what device, gauge are you using to get numbers of lean/rich?


__________________

learning to ride on 1993 TTR 250

Ex 1997 and 1998 Honda XR 250



Super Guru

Status: Offline
Posts: 1156
Date:
Permalink  
 



bore 28mm - intake 49.5mm / outlet 35mm
bore 30mm - intake 49.5mm / outlet 35mm
bore 32mm - intake 54mm / outlet 40mm
bore 34mm - intake 54mm / outlet 40mm

 

wide band air/fuel ratio gauge & sencer....






.



-- Edited by petenz on Monday 24th of July 2017 10:42:34 AM

__________________

 

.....................................................................................................

 http://www.kiwibiker.co.nz

Bikes... 06 TTR250 / 09 XT660R / 1977 Montesa Cota 348 MRR / 1979 Montesa H6 125 Enduro...

E-mail  xtpete1@gmail.com



Senior Member

Status: Offline
Posts: 127
Date:
Permalink  
 

Finally, all the parts (carb, jets, throttle grips with cable) arrived.

I manually made twin aluminium gasket 10 mm + 15 mm + two paper gaskets.

The air intake diameter of PWK carb seems to be 4 mm bigger comparing to stock, it fits but take some time to install it into rubber tube.

The fuel/air intake diameter of PWK is 1 mm smaller than standard carb.

I bought throttle grips with cable from https://www.aliexpress.com/item/1-Pair-Rubber-Throttle-Grips-Cable-For-Pit-Dirt-Bike-ATV-With-22mm-Handlebars/32621902548.html?spm=a2g0s.9042311.0.0.kmPSMV

The cable (plastic shield) is to short in the length and the working cable wire is to short too. So, I made my custom cable and it works great.

The carb itself came with two needles and 4 jets from https://www.aliexpress.com/item/SUPER-PERFORMANCE-RACING-Carb-Black-PWK-Power-Jet-Carburetor-28mm-30mm-32mm-34mm-Motorcycle-Scooters-dirt/32442944811.html

My 32mm carb looks the same as petenz owns.

Additional main and pilot jets came from https://www.aliexpress.com/item/New-12pcs-Set-Slow-Pilot-Jet-for-PWK-Keihin-OKO-CVK-30-31-32-35-38/32817317304.html, https://www.aliexpress.com/item/PWK-conversion-speed-glib-KOSO-main-glib-OKO-FCR-long-hexagonal-main-nozzle-main-jet-with/32242092310.html

I installed carb with the same settings as FBRConcepts described:

  • pilot jet 38 (this jet came with carb)
  • main jet 150.
  • The needles do not have any serial numbers. So, I took the longest one and set the clip in the middle (default factory settings).
  • The air screw is 1 1/2 turns
  • I'm living above 100-150m sea level.

 Bike setup:

  • Removed the snorkel rubber from air filter box
  • Rear cross tire brand new Pirelli 100/100/18.
  • Engine is strong. It produce almost 12Bar compression.
  • Exhaust head pipe is stock with removed restriction. Rear muffler is shorten Honda CRF 250R. 
  • Gearing is 13/48.
  • Fuel 95 octane
  • I believe piston is still stock

Carb in action... 

  • Bike starts OK cold or hot. I set the idle RPM to 1800. There is a slight stammer just off idle on rapid full throttle movement. If idle rpm is increased til 2500 there is no stammer. The same behavior was with stock carb.
  • Without clutch or help from me NO WHEELIES on rapid full throttle on 1st, 2nd gear. If I move my weight to the rear on the seat then on rapid full throttle you can do wheelie on 1 gear. But sitting closer to the tank it is impossible. I need to pull the handle bars to do that. That was same behavior with standard carb.
  • With new carb I did test drive 4 hours by riding in the forest and gravel roads, was jumping on the fallen trees. 

Comparisson ...

  • I think it performs pretty same like stock carb. Maybe there is 5% increase on power. I'm saying again maybe :)
  • This 32mm carb does not have fuel filter inside like the stock has. At the end of riding the rust came into the carb and it started to leak fuel and my trip has ended cause I did not have allen key with me.
  • This 32 mm does not have diaphragm, so it should be cheaper to maintain.  

Photos:

https://1drv.ms/f/s!AstbUZulPF2rgwJx1U21mkz3Affp

 



-- Edited by honda15i on Tuesday 22nd of August 2017 04:33:58 PM



-- Edited by honda15i on Tuesday 22nd of August 2017 04:43:11 PM

__________________

learning to ride on 1993 TTR 250

Ex 1997 and 1998 Honda XR 250



Senior Member

Status: Offline
Posts: 127
Date:
Permalink  
 

Today, I lowered needle by one position (clip is raised from center by one level) the hesitation increased from idle to rapid full throttle.

__________________

learning to ride on 1993 TTR 250

Ex 1997 and 1998 Honda XR 250



Super Guru

Status: Offline
Posts: 8557
Date:
RE: Alternative carbs for the TTR250 - 32mm carb
Permalink  
 


Chris and Arthur have both gone very quiet - is everything OK with your new carbs guys??

Bearing in mind that good s/h original TTR250 carbs are becoming increasingly hard to find, did you think any more about doing an after-market kit with all parts and instructions Steve?

Brian



__________________

Exeter, Devon, UK

http://www.ttr250.com  - The one and only dedicated TTR250 FAQ! 
 

TIP: For easy viewing bookmark the "Recent Posts" view - http://ttr250.activeboard.com/p/recent/ 



Senior Member

Status: Offline
Posts: 127
Date:
Permalink  
 

I switched on oem carb.
However it has also problem now - on high rpm it bogs. Main jet or needle needs cleanup/Adjustment

__________________

learning to ride on 1993 TTR 250

Ex 1997 and 1998 Honda XR 250



Super Guru

Status: Offline
Posts: 8557
Date:
Permalink  
 

honda15i wrote:

I switched on oem carb.


Can I ask why you gave up on the other carb please? 



__________________

Exeter, Devon, UK

http://www.ttr250.com  - The one and only dedicated TTR250 FAQ! 
 

TIP: For easy viewing bookmark the "Recent Posts" view - http://ttr250.activeboard.com/p/recent/ 



Senior Member

Status: Offline
Posts: 127
Date:
Permalink  
 

I had problems with chinese carb.
It was running great but suddently started
1. Bogging while riding in the middle of ride
2. Started to leak fuel at the end of the ride

I sorted the leaking problem - bowel valve was not closing properly
I could not get rid of bogging problem
Cleaned carb couple times
Changed jets, needle and needle clip position. I was tired with this chinese rubish...

__________________

learning to ride on 1993 TTR 250

Ex 1997 and 1998 Honda XR 250



Super Guru

Status: Offline
Posts: 2644
Date:
Permalink  
 

We all think that the Chinese stuff will be a good/ cheap alternative and come un-stuck! Don't get me wrong there are some things that are good, but it seems engine components and other critical parts are not up to scratchcry

Shame really as the cost of the genuine gear is a lot more, but then we never have trouble with it.



__________________

totallyttrs.com

 



Super Guru

Status: Offline
Posts: 1156
Date:
Permalink  
 

LOL... mine done the same after about 6 or 7 rides....
what it was is the choke plunger rubber shrunk and let air though..
so i sat a 1mm section O-ring in the bottom of the choke hole...
so far no more issues...



.


__________________

 

.....................................................................................................

 http://www.kiwibiker.co.nz

Bikes... 06 TTR250 / 09 XT660R / 1977 Montesa Cota 348 MRR / 1979 Montesa H6 125 Enduro...

E-mail  xtpete1@gmail.com



Veteran Member

Status: Offline
Posts: 31
Date:
Permalink  
 

I read through the post on using an alternative carb on the TTR 250, so last fall I ordered a 32 mm KOSO carb, an appropriate throttle cable and new twist throttle and pilot and main jets as per suggestions for jetting on this sight.

Now that its installed and I have been running it on back road rides here are my suggestions:

1. its a really cheap carb in the way its made.  the chrome was flaking of the slide new, the jets supplied had no markings on them.......either pilot or main jets, and it came with one needle that is unmarked, on two screws holding the float bowl on.

2.  When i had built my spacer block and went to install the carb I discovered the inlet end of the carb is really no the correct size for the stock Yamaha rubber boot, after fooling with it I was pretty sure it would work ok anyway.  The bell mouth of the carb is too big to fit the stock Yamaha air cleaner snorkle.  I chucked the carb in  my lathe and machined it down to about  2.450 inches, fits snug but doable now.

3. after trail and error jetting and several rides at 60 degree F temps  3200 -4500 ft altitude here in Montana the best jetting I have found is :  148 main jet,   35 pilot,  needle down as far as it will go ( so clip in the top notch on the needle providing leanest running situation ). 67 miles to the gallon on the ride of 127 miles of dirt road and mud and snow section, so good mileage I would judge.  Runs clean, idles, starts with just a little choke rolling it out of warm garage.

4  for a really cheaply mfg carb it runs great..............for how long ?  its simple,  you can change jets easily with the stock tank without removing the carb from the bike.......I loosen carb clamps, tilt carb out, remove slide, then tilt car in and change main jet through the 17mm nut, or remove float bowl to change pilot jet.

5.  it used stock keihin pilot jets, and small round Mikuni main jets, I sorted through 40  or 50  old needles and tried some 4dh4,   4dh2,   dh4-82,  all two stroke needles, all cleaned up the fat spots but where too lean in the mid range and while it ran clean and smooth it had no balls, stock needle taper works best for my bike.

6 no engine mods on my bike,  more air flow in the air box, stock pipe but with a YZ250f  aftermarket quiet insert.  Very quiet bike so the pipe maybe a little restrictive.  UP side I have my bike geared 13/44 for overlanding, and it pulls super good at high gear low throttle .  When I drop main jet or try another needle, the fat strong low throttle pull goes away.

7. carb is fitted with a power jet, and the jet in there  as per has no markings ?  I have not confirmed yet the power jet performs at all or supplies any fuel on top end.

 

Now that I have ridden the bike on day  long rides, I have lowered my pilot jet size to a 32.  better throttle response in low mid range, cleaner running.

93 miles on mostly slow dirt road with no elevation change,  I used 1.1 gallon of gas.......so   84.5 miles to the gallon, my gps said   19.2 mph average.



-- Edited by sledman 1 on Tuesday 1st of May 2018 05:48:16 PM

Attachments
__________________


Veteran Member

Status: Offline
Posts: 54
Date:
Permalink  
 

well done!!  mine is still running fine after almost 2 years now, i do have to rejet between summer and winter but for such a basic carb that's to be expected..

 

sorry i dropped off the face of the planet, it took a while to heal up after the fall and then i was super behind with work here and then other life things got in the way, went about 7 months without a ride and then my dad got sick and life threw another curve ball so he can no longer ride the bike and I just take it out for quick spins in the neighborhood.  I would love to try and get it plated an use it as a dual sport as its pretty much brand new again after all the work and would make for a very fun local trail bike with no need to load in a truck.

 

we shall see!  hopefully others have been updating carbs if needed, doesn't seem like too many people got involved after testing.

 

Chris



__________________


Veteran Member

Status: Offline
Posts: 54
Date:
Permalink  
 

oh and this carb definitely adds more power!  would love to try out a shorty header setup with the better breathing carb on, i imagine the combo along with the fmf pipe and airbox mods would net some nice gains!



__________________


Newbie

Status: Offline
Posts: 2
Date:
Permalink  
 

Just thought I would bump this up as oem carbs get harder to get cheapily.

Anybody still running one of these?
Are the spacers available from anywhere?

__________________
«First  <  1 2 | Page of 2  sorted by
 
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard