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Power band remap on fresh rebuild?

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YO! 

Rebuilt my 03 RM 250 and it has half the bottom and midrange it used to have. It's all top end, shes a screamer now. Plenty of power and a fun bike, but i mis that bottom end snap. Bike had an oem piston. everything was oem when i bought it, put around 90 hours on it and did a fresh up. Needed a top end bad. Broke it in with a 2-3 min warm up, shut off for 2 mins, warmed up again, 90 sec idle then a quick 1/4 to 1/2 throttle 25 min ride up a rockey abandoned service road,

PV at stock
Reed stuffer in
Wiseco top end kit with athena gaskets

Is it the wiseco vs the OEM cast that is making the power difference? Nothing else has changed...the bike WAS swamped twice BEFORE the rebuild, but it ran great after dumping all the watter out THAT ridding day. Is it the silencer that needed to be repacked? (stock exhaust, packing was super goey and wet from swamping)

vid of bike, 4 hours run time after rebuild.

https://scontent-1.2914.fna.fbcdn.net/hvideo-xpf1/v/t43.1792-2/10396750_10202218194802273_1940731017_n.mp4?oh=f9f56d331773fe8c588acb7a56a17b6e&oe=5390156D

Edited by Afrothunderkat

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That "break in" you did probably was not that great for seating the rings. Cruising isn't the best thing for break in.

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That "break in" you did probably was not that great for seating the rings. Cruising isn't the best thing for break in.

I had my main ridding buddy with an 04 RM 250 that did a top end and PV clean with me and we did the same break in procedure. His bike has ALOT more grunt than mine, and before the rebuild it was the complete opposite. There was a few seconds of WOT here and there.

Edited by Afrothunderkat

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Just wondering... Did you install the power valve correctly?

There is only one way for it go back togeather! I was using my manual (for an 06) and my buddy was right there doing his 04. his looks way diff though. (previous owner nadded the bike and we think it has an 04 bottom and 06 top end.)

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PV is stuck open

Just cleaned it, and only 1 turn preload. Now that you mention it, the motor is alot like my 85 non PV ATC 250R. 

How would the PV be stuck? I JUST cleaned it and all the linkage was in good shape?

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I would take it back apart and re-check your power valve. It does sound like it's stuck open. 

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Just cleaned it, and only 1 turn preload. Now that you mention it, the motor is alot like my 85 non PV ATC 250R. 

How would the PV be stuck? I JUST cleaned it and all the linkage was in good shape?

 

 

1/2 turn preload is stock, take off the  front and side PV covers and manually operate it to observe whats up.

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1/2 turn preload is stock, take off the  front and side PV covers and manually operate it to observe whats up.

 

Yes, that's easiest way.

 

However, OP says it has half the bottom end it used to have- I've had a PV stick open and it had no bottom end at all, was virtually unrideable. Hmmm.

 

Other ideas... Definitely correct year piston and installed the correct way around?  Timing checked? Pilot jet cleaned? Reeds ok? 

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Yes, that's easiest way.

 

However, OP says it has half the bottom end it used to have- I've had a PV stick open and it had no bottom end at all, was virtually unrideable. Hmmm.

 

Other ideas... Definitely correct year piston and installed the correct way around?  Timing checked? Pilot jet cleaned? Reeds ok? 

Piston is correct way, not sure of year, just bought a wiseco off ebay for $115. Timing, and jetts not touched. I wanted a before and after so i left the rest of the bike alone.

Top end kit... http://www.ebay.com/itm/390734921297?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

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Yeah that looks fine. Did you remove the stator and change timing at all on rebuild? Might as well repack that silencer and check pipe for blockage since these seem to be the only things that changed.....

By having too much preload on your PV you should of had more bottom end. It still smells of PV to me..... did you manage to get the front main valve cover open and observe it? I've had one of those little springs break and periodically hang the valve open. I chased jetting for a week before I pulled the cylinder to discover that. It was the worst to diagnose because sometimes it hung up, other times it worked fine.

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Yeah that looks fine. Did you remove the stator and change timing at all on rebuild? Might as well repack that silencer and check pipe for blockage since these seem to be the only things that changed.....

By having too much preload on your PV you should of had more bottom end. It still smells of PV to me..... did you manage to get the front main valve cover open and observe it? I've had one of those little springs break and periodically hang the valve open. I chased jetting for a week before I pulled the cylinder to discover that. It was the worst to diagnose because sometimes it hung up, other times it worked fine.

Nope, no timing change. Deff going to repack, I drilled out all the rivits and will be using alen head bolts to hold it together. Also removed all the black paint and high heat clear coated the entire exhaust, looks pretty good. I thought less laod = more bottom, the spring can open easier....But more turns = more bottom end?

Did not take the cover off, didn't want to dig that deep but I will just to make sure. I was running 2 exhaust washers, now only one. I was running one before the rebuild and thought hey, ill try two, why not. I took it out, and went for a test ride. Nothing changed.

Do reed cage stuffers come stock in 03? my buddy has an 04 and doesn't h ave one. Also, Do they bump up bottom end? or top. 

Are you guys sure it's just not the wiseco vs the oem weight?

Edited by Afrothunderkat

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PV staying closed = higher compression = more bottom end. 

Piston won't make a difference I run Wisecos and have heaps of bottom end.

03 came stock with no spacer. I have tried the spacer and found while it gave me more bottom end, I lost too much throttle response. I tried it for about a month and then pulled it.

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Wiseco pistons are normally a little bit heavier than OEM, if your good you "might" be able to tell the difference between the two when riding.  It would feel like you just added a 1 or 2 oz flywheel weight.  Either way, it would feel stronger on the bottom not the top.

 

My money is still on the power valve or the timing.  Assuming that you didn't mess with anything else and that your reeds are in good shape, and if the reeds are stock they need to be replaced (they don't last forever).

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Yeah, this isn't making sense.

I'll take pictures of my reed stuffer and reed cage. I'm not sure it's the 03 cage. I am 99% sure the reeds are stock from 03.

Also, I'll pull the front cover off and take a look. There is only one way to install the main PV slide correct? It all goes together ONE way correct?

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