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Top End Speed - Less that Before ... ?

5K views 28 replies 13 participants last post by  ToolmanJohn 
#1 ·
Greetings all,

So I've been riding my TW around for 2-3wks or so now after I had done some adjustments to the carb and had added the slip on, and thought my daily riding is still quite fun, the bike feels decent, and has no issues starting up/etc, I have noticed some change in top end speed.

Previous to doing anything at all to the bike, I was able to easily get up to 55/60 and without too much more effort get to 70+ (topped out at about 73mph a couple of times) with pushing it, but not that much. Now I know keeping it at 70+ for too long is not a great idea, but I know much larger folks that me have stating that their stock TW sits at 55-65mph pretty easily. I weight about 138lbs. I would like to do a little longer camping rides, and would like to feel confident on cruising 55-65ish for at least periods of time.

Recent adjustments to bike:
• Swapped out the stock pipe for a slip on DG.
• Adjusted the main jet from the stock 126 to a 130 (Pro-cycle Jet Kit)
- recommended to go to 130 by a few other folks in the Central Texas area
- Our elevation is approximately 425 feet (130 m) to approximately 1,000 feet (305 m) above sea level
• Adjusted the idle/air screw from stock to 3x turns
- had it at 2.5, but was experiencing a little bit o rough riding, and went to 3x and it seems much nicer/consistent

Since then I have ridden off-road and a few different rides around town with folks, as well as several hours alone cruising back streets after work. The bike has had several hundred miles put on it since the work above was completed. Though during some of those rides I have attempted top speed tests, and have yet to be able to get back up in the 70s, and now 55 feels like it's more/less all it's got. I did at least get close to 65mph last weekend, but again, it felt like it was at it's limit more/less. Getting into the 60s seems much more of a task that it has previously.

Any thoughts on what could be causing that? Could it just be that it just so happens when I've been testing top speed there has been too much wind and/or uphill on my routes—aka I'm crazy? I feel like I've done it enough where I'd be able to hit that top speed at some point, or at least feel a bit more comfortable going into 55-60. The first times I tested it anI did not have to push it as hard as I feel I've been pushing it the last couple of time. In fact, today at 55 I couldn't really seem to get it to go much more that that.

Side note: One thing I did think about, was that through removing the carb several times, I also detached the throttle assembly wheel on the carb multiple times. I had tried to remove the actually throttle cables once, and decided I felt it was just easier to remove the assembly—got pretty good at getting that spring back in place (or I think I did). Anywho, in my attempt to "remove the cables" vs. removing the wheel altogether and leaving the cables attached, it's possible I made an adjustment that could effect something. It seems to have the correct about of free place, and seems to still adjust all the way open/close.

I am no mechanic (and usually not a complete idiot), but am trying to tinker, learn and do as much as I can on my own. Any thoughts/suggestions/recommendations would be greatly appreciated :)
 
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#5 ·
I never try to fix anything that is not broken to begin with. Sounds like your TW was running perfectly fine before you made the changes so whatever changes you did have resulted in less than positive performance. It can be fixed and with the parts you have added but it will be a process of hit and miss to get all the new stuff dialed in.

GaryL
 
#6 ·
I'd tend to agree with Gary - but i would add that first you have to dial back everything you did to change things. Taken one step at a time, you will be able to tell what change made the speed decrease - at the moment, you have no way of knowing where to start

Everything is fixable - but you have to know where to look for it ....
 
#7 ·
My guess is the jetting. More fuel does not necesarrily mean more power, it's more of a bell curve- if you're putting more fuel you still need the correct amount of air to get that ideal 14.7 ratio for more power. But even a 10% power upgrade [which is unlikely] would still be less than 2 horsepower. I'd suggest, like a few others said, to go with a smaller jet and see how that works for you.
 
#8 ·
Thanks all. Makes sense. I'll spend some time with it this weekend. I'll likely jump down sightly in my main, and go back to 2.5 turns on the air screw.
 
#9 · (Edited)
Greetings all,

So I've been riding my TW around for 2-3wks or so now after I had done some adjustments to the carb and had added the slip on, and thought my daily riding is still quite fun, the bike feels decent, and has no issues starting up/etc, I have noticed some change in top end speed.

Previous to doing anything at all to the bike, I was able to easily get up to 55/60 and without too much more effort get to 70+ (topped out at about 73mph a couple of times) with pushing it, but not that much. Now I know keeping it at 70+ for too long is not a great idea, but I know much larger folks that me have stating that their stock TW sits at 55-65mph pretty easily. I weight about 138lbs. I would like to do a little longer camping rides, and would like to feel confident on cruising 55-65ish for at least periods of time.

Recent adjustments to bike:
• Swapped out the stock pipe for a slip on DG.
• Adjusted the main jet from the stock 126 to a 130 (Pro-cycle Jet Kit)
- recommended to go to 130 by a few other folks in the Central Texas area
- Our elevation is approximately 425 feet (130 m) to approximately 1,000 feet (305 m) above sea level
• Adjusted the idle/air screw from stock to 3x turns
- had it at 2.5, but was experiencing a little bit o rough riding, and went to 3x and it seems much nicer/consistent

Since then I have ridden off-road and a few different rides around town with folks, as well as several hours alone cruising back streets after work. The bike has had several hundred miles put on it since the work above was completed. Though during some of those rides I have attempted top speed tests, and have yet to be able to get back up in the 70s, and now 55 feels like it's more/less all it's got. I did at least get close to 65mph last weekend, but again, it felt like it was at it's limit more/less. Getting into the 60s seems much more of a task that it has previously.

Any thoughts on what could be causing that? Could it just be that it just so happens when I've been testing top speed there has been too much wind and/or uphill on my routes–aka I'm crazy? I feel like I've done it enough where I'd be able to hit that top speed at some point, or at least feel a bit more comfortable going into 55-60. The first times I tested it anI did not have to push it as hard as I feel I've been pushing it the last couple of time. In fact, today at 55 I couldn't really seem to get it to go much more that that.

Side note: One thing I did think about, was that through removing the carb several times, I also detached the throttle assembly wheel on the carb multiple times. I had tried to remove the actually throttle cables once, and decided I felt it was just easier to remove the assembly–got pretty good at getting that spring back in place (or I think I did). Anywho, in my attempt to "remove the cables" vs. removing the wheel altogether and leaving the cables attached, it's possible I made an adjustment that could effect something. It seems to have the correct about of free place, and seems to still adjust all the way open/close.

I am no mechanic (and usually not a complete idiot), but am trying to tinker, learn and do as much as I can on my own. Any thoughts/suggestions/recommendations would be greatly appreciated :)
I don't see any mention of the needle. Shimming didn't work for me. Get the 5LB-14336-00 used in Australian and South African TWs. Set clip to center position.

https://www.partzilla.com/product/yamaha/5LB-14336-00-00

Also put in the #34 pilot jet. 5LB-14342-17-00 JET, PILOT (#34)

https://www.partzilla.com/product/yamaha/5LB-14342-17-00

Remove the snorkel from the airbox to move more air through that DG. Very important. Just pull out (rubber duct assembly). Stock air filter. No holes in airbox cover.

Drill out hole on slide diaphragm will a 3/32 or #39 bit.

My air screw with the above changes is at 1-3/4 turns.

Main is a 132. 130 was not enough. 135 was to much. I'm at about 2500 feet elevation, tested at 0 ft to 4500 ft with no issues.

That's my setup. Working great for me with my DG and 2006 CA carb.

No flat spots or hesitation at all. Smooth from bottom to top. More power EVERYWHERE! Stock is not even close.

Took me a VERY long time to get this correct. Enjoy.
 
#11 ·
Quite a lot of mods to get that sucker dialed in. Thanks for the info. I'm probably going to try and go slower this time, as the first time I did EVERYTHING at once.

I didn't touch my needle—still using stock. I did get the Jet Kit from ProCycle, which does have a replacement needle that I believe is stock—what's the difference in the other needle you recommended?

My jetting kit came with a #34 pilot, so I can easily try that.

For the air-box snorkel—that is under the seat? I've never fussed with the air-box.

Regarding the recommendation to drill out the hole in the slide diagram—the center hole that the needle sets in, or the other one off center from that one? I'm guessing that is also to let more air in?

Thanks again.
 
#10 ·
Here's what I have on mine (also in Austin) and it runs perfectly. Easily pulls to 70 and tops out around 80-82 with a bit of a tailwind (that's more the piston and cam, although I ran this same setup on stock engine and it also ran great)

32.5 pilot (stock is 31). The one in there is a generic, although I seem to remember seeing you can get a Yamaha 32.5 if you order the pilot jet for a Raptor 90.
135 main (stock is 126. I ran a 130 for a while and it was good with the stock engine, but I found with the cam it seems to like a little more fuel in the top end)
Stock needle, no shims. Tried shimming it, just got worse gas mileage for no noticeable benefit.
Couple holes in the airbox lid. This is much easier to "undo" than removing the snorkel which is completely impossible to get back in once you yank it out. The holes can easily be plugged with a plastic bung, or just covered with tape if you're considering going boating with it and want the higher air intake point.
Fuel screw about 2 turns. At 1 3/4 it'll start popping on decel a little. 2 turns, no popping at all.
FMF slip on, w/ XT225 headpipe (identical, just shiny)
Wiseco 10.25:1 piston, stock 67mm bore
Webcam stage 1 (340a grind)
15/47 gears. 60-65 is an easy cruise with power to spare.

I find removing the two cables about 400x easier than taking the entire wheel off and fighting to wind the clockwork spring back up again. I can get the carb off or on the bike in less than 5 minutes.

You're welcome to stop over some evening and we'll get it dialed in.
 
#13 · (Edited)
It's weird. I had no luck with the airbox holes, but at that point I didn't have the slip on yet.

My current setup from the earlier post also has no popping at all and great plug color.

I can pull 72, zero to 60/65 is no problem (14/45). Not a good as your cam/piston ($$$$) setup but great for stock. No flat spots in the acceleration either.

Russ rode my bike awhile back and told me it was one of the nicest jetting setups he'd ridden. I was really proud of that coming from him. Lizrdbrth approved LOL.
 
#17 · (Edited)
Cam/piston isn't really as $$$$ as you'd think. Costs less than a slip-on. Think the piston was $80 and the cam was $150(plus refundable $150 core charge for your stock one). Took maybe 2 hours total to install. The pistons are readily available, although Webcam does not keep TW cams in stock anymore (they said low demand), so there's about a 2 week lead time to get one. Still available, just on a special-order basis.

Changing the piston and cam sounds scarier than it really is. These engines are about as simple as they get.

Monday/Tuesday/Thursday evenings I'm usually free. I think I gave you my number last time at the bike night, just shoot me a text and I'll let you know if I'm around.
 
#20 ·
Awesome. That is way more reasonable than I would've though actually. I'll definitely take that into consideration then ... if not immediately, certainly a future upgrade :)

I do have your number from the bike night. Tuesdays and Thursdays generally work well for me.

I looked on partzilla at the Raptor90s to try and find that #32.5 pilot. The newest models 2016-2018 don't list the pilot size for the jet in their parts listings:
https://www.partzilla.com/catalog/yamaha/atv/2017/raptor-90-yfm09ryxhw/carburetor
https://www.partzilla.com/product/y...?ref=8878b0666dca4255fefb4d212912d0014bdac41f

The older models seem to all have a #32, not #32.5:
https://www.partzilla.com/catalog/yamaha/atv/2013/raptor-90-yfm90rdl/carburetor
https://www.partzilla.com/product/y...?ref=b5ed90770a912750370c045b364484c71df195f9

When I do a general search for a #32.5, there are quite a few options, but I'm not seeing ones that necessarily match the exact size to fit the TW ... do you remember which one you purchased?
https://www.partzilla.com/search?pg=2&q=32.5+pilot+yamaha

I'll get the pilot jet .... and consider if I can spend another $300ish for the piston/cam right now, and then get back to you.

Thanks!
 
#21 ·
If your jet kit came with a 34, you can go with that, you'll probably just end up with a little less turns on the pilot screw vs if you had the 32. The jet size is the "coarse" adjustment, the fuel screw is "fine" adjustment. a 31 pilot with 3 turns is probably about the same amount of fuel delivered as a 34 pilot with 1.5 turns. Techinically you can infinitely adjust this from no fuel (screw closed) up to where you want, but generally the screw's effective tuning range is from 1 to 3 turns. Less than 1, or more than 3, means the jet size should be adjusted accordingly.
 
#22 ·
If your jet kit came with a 34, you can go with that, you'll probably just end up with a little less turns on the pilot screw vs if you had the 32. The jet size is the "coarse" adjustment, the fuel screw is "fine" adjustment. a 31 pilot with 3 turns is probably about the same amount of fuel delivered as a 34 pilot with 1.5 turns. Technically you can infinitely adjust this from no fuel (screw closed) up to where you want, but generally the screw's effective tuning range is from 1 to 3 turns. Less than 1, or more than 3, means the jet size should be adjusted accordingly.
Groovy. Thanks. Going to go ahead and order a 132main as well. That'll give me a pretty complete set of jets for future tuning/etc. Now I've just got to consider if I want to do the cam/piston upgrade now. Gotta talk the wife into it since I've already spent a bunch of $$ on this puppy :)

Thanks again. Talk soon.
 
#23 ·
I will make a suggestion to you Tyler as you work your way through carb upgrades. You can often fine original carbs on either Ebay or from other members here. I suggest you buy a second carb and do your upgrades on it so you can easily swap the upgraded one in and out and be able to determine if the changes you made help or hurt your performance. When I was actively riding my TWs I always had a carb that I knew was running perfect and I played around with the spare one to see if I could get it dialed in a little better. Carbs are funny ducks and the slightest change made inside can produce varying results so I loved having one carb I knew was on the money at all times. I also always had a fresh carb to air box boot on hand because this connection is the most likely one to get a tear or leak in. To be very honest with you and others reading this thread, the very best running TW I ever had ran the very best with a brand new totally stock OEM carb and all the other changes I ever made on the spare might have done a little for the overall performance but not enough to make me think I knew better than the Yamaha carb designers. Shimming the needle and changing jets did get the bikes to start easier and perform a bit smoother but never really gave me much of a noticeable boost in overall performance. It just seemed to me wherever I gained in one area I lost something in another and it was usually in the top end speed the bike could run at. Better response in the first few gears was nice but I usually lost a few MPH on the other end. A few guys here have gotten their carbs dialed in to where they love them but I just never found that sweet spot in all the changes I did over the 10 years of messing with TWs. Changing the mufflers was about the most useless thing I ever did and I always went right back to the original one for one reason or another.

GaryL
 
#24 ·
Thanks for the advice Gary. I did actually buy a back-up carb from Radracing that has the stock settings—though I did remove the little spring that sits on the white clip of the needle. I lost the stock one the first time I took the carb apart. I did get some replacements... so that's my baseline carb for now I guess :)
 
#25 ·
Tyler...

The only "Radracing" Google finds are BMX & T-shirt shops.

Got a different spelling?
Thanks!
 
#26 ·
#27 ·
Thanks Tyler.
 
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#28 · (Edited)
Reasons for fuel mixture changes (generally richer), include:
1. To operate properly, such as opening up the mixture screw to 2 1/2 to 2 3/4 turns so it will idle and start better.
2. To avoid burning a hole in the piston at sustained WOT.
3. On a CV carb, shimming or replacing the needle if the carb bogs/hesitates on the transition from idle to mid-range.

At low elevation, a larger main will probably operate OK, but may blubber at altitude and the richer mixture may be slightly less fuel economy and slightly less HP.

How did spark plug look, before and after the mixture was made richer?

Although I strongly disagree with Nightrider regarding drilling the slide ***, this link is an excellent troubleshooting guide for a constant vehocity carb (disregard the accelerator pump part):

http://www.nightrider.com/biketech/carb_troubleshooting.htm

*** http://xlforum.net/forums/showthread.php?t=2071846&page=4 see post 13
 
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#29 ·
Beyond obvious jetting changes, as all have said.

Maybe some bad gas or trash/debris in the carburetor which is blocking jets. If you have the carb out, blow out those passages with compressed air. And make sure all the little rubber bits are intact as well. Some of them are so easy to lose and not realize they went missing.
 
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