125-200cc First ride 09 WR 125 and the bog

[BillO]

Thanks Motosprtz, that’s just about what we have right now.

Now, got a question for y'all.

Here is the set up:

• Engine: 2008 CR125 bottom end with a EG 144 (from a 2006 WR125)
• Carb: TMX with 35 PJ, stock CR125 needle in 3rd position, stock slide, 450 MJ
• PV: White large spring with small green, PV linkage at ¾

Symptoms:
Pulls very hard throughout most of the range, but has a small flat spot just before she gets on the pipe hard. It’s not a bog, just a tiny range of about 500 rpm where there is no increase in HP. This flat spot is not throttle position dependant, only RPM dependant (will happen at ¼, ½, ¾, full throttle).

The net effect of this is:

• Will not pull through this region under high loads in 5th and 6th (sand washes, long rises, etc…)
• Delayed acceleration when exiting obstacles (log crossings, rock drops, rock gardens, step-up jumps, etc…)
• Balking while entering tricky obstacles.

Most of the time the symptoms can be overcome with a quick fan of the clutch, but for the type of riding the bike is used for (FIM style enduro), this is not always possible.

BTW, neither of the 125’s that donated parts to this bike had such a problem.

Any ideas?

 

[wallybean]

BillO,

First thing is try it adjusted all the way to the top. If it eliminates the flat spot and doesn't cost you noticeable top then you are set. If it doesn't work then try the yellow spring with the green inner spring at 3/4 of the way to the top. Then try this setup all the way to the top. If it is still not solved try the stock spring with the green inner spring at both positions. If you are using an 06 WR 125 cylinder then you have the larger old style power valves. They shouldn't have quite the problem with a bog as the newer power valves. While some WR125's don't like the softer large spring, mine is the opposite and works great with no flat spot using the yellow/green at 3/4 adjustment on linkage. Of course I modded my power valves further and my bottom and mid is substantially better than with the stock grind. Lots of stuff to try and so little time.

Walt

Another thought is that when EG re-grinds the power valves he only grinds the face and you actually end up with a wider sealing surface than stock which actually lowers the effective height of the exhaust port before the power valves open. I found that for optimal results the power valve sealing surface should be 2-3mm wide. To accomplish this you need to re-grind the bottom side at ~60 degrees to the sealing surface. The finished grind would leave a sealing surface that wide and parallel the top of the power valve.

 

[rockdancer]

It may be the power valve but have you also tried leaner carb settings? my WR 08 has 380 main 27.5 pilot and 2nd slot for needle works much better than with richer pilot and needle setting.

 

[BillO]

Thanks for the responses guy's. I'll have to leave well enough alone for this weekend. Pat (my son) is racng the bike on Saturday. His next serious race is not until July 3rd. We'll try some of your suggestions in the interim. I have also ordered up a PWK and some extra jets from Motosportz. Once we have time to get it out for some tunning over the next two weeks, I'll let you all know how we faired.

View attachment 5076

 

[skid]

Symptoms:
Pulls very hard throughout most of the range, but has a small flat spot just before she gets on the pipe hard. It’s not a bog, just a tiny range of about 500 rpm where there is no increase in HP. This flat spot is not throttle position dependant, only RPM dependant (will happen at ¼, ½, ¾, full throttle).

Any ideas?

interesting I have an 08 cr 125 top and bottom end that e g 144'ed. I have had little time on it and have been messing with the jetting somewhat. I have noticed this flat spot. I tend to ride tight woods and and don't really bump into said flat spot in the tight stuff but did notice it on dirt roads,. I haven't done anything with springs or adjusting the p valve lever thing. my 144 was set up for more bottom and mid. I'm finding that I can motor through the tight stuff on just the bottom end.

 

[BillO]

So, here's the thing. Pat's race saw him come in just 40 seconds out of a podium spot in the pro class. That's 40 seconds out of 59 minutes and 30 seconds of race time. He did not experience the effects of the flat spot in the extreme or MX special tests put hit it continuously in the enduro tests (single track that made up 28 minutes of that 59) whilst transitioning on and off the pipe. Most noticed in those short bursts between turns in rapid succession. Not enough time to fan the clutch, but no acceleration due to that nasty little flat spot. So this alone might have cost him a trip to the podium. Rats!

I was thinking. That CR pipe is just a bit different than a WR pipe. Now, we asked EG to tune that top end for more bottom and mid. This leads me to some more questions.

• Might it be that there is a miss-match between the porting and the pipe?
• Would a pre-2009 WR pipe be tuned a bit lower and possibly work a bit better? (Needs a different lower mount point, but that can be fixed.)
• Does anyone have experience with the FMF pipe? Does it boost low end or high end?

All thoughts appreciated,

Bill

 

[BillO]

It may be the power valve but have you also tried leaner carb settings? my WR 08 has 380 main 27.5 pilot and 2nd slot for needle works much better than with richer pilot and needle setting.

Stock it had a 400. This was a little lean once the 144 went on it. Not terribly lean, but enough that if felt like it was wheezing. With the 450 it pulls harder WO and the plug looks better, at tad rich, but better than the stock. I'll try a 440 tomorrow, but really do not want to spend too much time friggin with the TMX. Not on this bike. He has another '06 WR for a practice bike that I will do more TMX tuning on. Once I get the motor back, that is.

This is another one we had EG'd, but after 4 hours the plating flaked of taking the top and bottom end at the same time. The cylinder is back with EG to send back to Millenium, the bottom end is with the shop....it will be a while...

Thanks for the response rockdancer.

 

[BillO]

@Walt

You've given me a lot to try, some easy, that I'll do this week, some not so, but very valid. For that stuff (pull the PVs and grind), I'll have to wait until August.

Right now, the Yellow spring is in the '06 WR, which is in the shop. You don't by any chance sell these springs individually?

 

[BillO]

@skid

It's nice to hear I'm not nuts. Thanks for chiming in.

The flat spot was worse with just the stock spring in it. Putting in the wallybean White-Green combination improved it from something like 1000 rpm wide to just 500. The PV lever was at 3/4 from the get go. I'll try shifting it a bit either way. It's a 10 minute exercise, so I don't mind this.

 

[wallybean]

BillO,

I had the same flaking problem with my EG kit and it is directly related to lack of chamfering of the ports and also the exagerated relief of the exhaust port bridge. I personally don't want the bridge area relieved. That is why there are small holes in the piston skirt to cool and lubricate this area. I don't know who's responsibility it is to chamfer the ports but it wasn't done on mine and caused complete failure of the lining.

Now I don't believe in sending my bad parts back to the responsible party even if it is free. I just had George at uptite fix the problem when he was looking at the possibility of boring the 09 125 cylinder to 167. Has run flawlessly since with the PWK added.

I am not in the business of retailing stuff, I am a golf course superintendent who rides on those rare occasions I have time. If you are interested contact Hall's or ScottyR. I just got done enjoying my first complete day off in over a month.

Walt

 

[BillO]

Walt,

Yeah, I questioned Eric on that bridge relief. To me it seems excessive and not well finished. If it were half as deep and had a polished transition into the bore it would be much better. I think with the added breath of the 144 a little of this is a good idea, if well done. As it stands, the hard, sharp edges of the ring would come into dispute with the equally hard and not so smooth transitions of the bridge relief. Something has to loose that battle.

Ports are pretty well chamfered on the current jug. The bad one, I'm not sure about the transfers, but the exhausts were done. However, just over the left exhaust port and bridge is where the flaking occurred. Could just have been an anomaly.

One the spring, don’t give it a second thought. Just aksin’, as it were. I know Scott very well. He races with my son from time to time and we’ve bought all four of our Husky’s from him. I can certainly afford a whole kit and will give him a call this week.

Also, I know the ‘ride when you can’ routine. I run support in Canada for a major software company, so limited off time is the norm. I can well empathise with you on that.

Thanks for the input.

 

[Motosportz]

For reference on the 144 kit / jetting (also posted / updated in 125 jetting sticky)...

Note: Swapped carb from stock Mikuni 38 to a PWK 38 and installed a OEM 144 kit. Stock PV springs.

Year & Bike Model = 2009 WR125
Carb = Keihin PWK 38
Pipe & Silencer = 04 Doma pipe and PC SA
40:1 Amsoil
Temperature range (deg F) = 55-75f
Elevation (feet) = 50-3500
Main jet = 172
Pilot jet = 45
Needle = JD red
Clip position = #4 (one richer than middle)
Air screw setting = 1.5 - 2
Slide = 7

Runs hard bottom to top, no bog. VERY happy with performance since the PWK swap. Super happy since 144 install

Note: I have the powervalve actuating arm with the adjustment near the top.

 

[skid]

Bill I'm running an fmf pipe. My 125 blew up the first ride I put it on. was running a 390 main wfo 6th gear 50 F. (stock tmx)quit not long into run ... say less than 10 seconds. running the same pipe on the 144. My guess at this point is it gives some more bottom.

not liking this flaked coating stuff I'm reading ... guess I'll have to keep an eye on that