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Wiseco High Compression Pistion-Knock?

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Just picked up a 2006 RMZ-450.  PO had put in a wiseco 13:1 compression piston and stage one cams.  He could not start it for the life of him and sold it to me cheap!  The thing is immaculate!  Old cams were like new, hardly any boot ware on the engine covers.  So this is what I found LOL

  • Chain Masterlink was on backwards -First warning sign
  • exhaust valve timming retarded 90 degrees (Doh!, thats why it did not start!)
  • Piston ring in upside down!
  • piston pin clips installed with opening right inline with cutout
  • Second wiseco piston was on the bench (he ordered two by accident).... my gain :ride:
  • I used at least 7 heli coils in various places.

Those were his mistakes, These were mine (thinking the bike was nearly new, based on look and cam and head condition)

  • Visual inspection of cylinder (looked beautiful)  Did not measure
  • Visual inspection of Crank (possibly a hair of up and down play???, felt this before on other bikes though)
  • there was a very slight mark in piston from one exhaust value (I removed the valve and inspected it)  My V blocks were too big to allow a check of the valve stem runout, so I installed it did a leak test on all 4-valves (passed)
  • don't know how to spell piston (see title of post)

Ok so it runs Awsome. I  took it out and it seems to knock (not ping) when its moving ie under load (not on the stand).  I'm nearly sure its in perfect time with engine RPM, and its not all the time, just sort of as your midly accellerating under half throttle

Rode for 2 hours easy and then started to give her and its a monster, when riding hard I don't seem hear the noise as much Maybe because I'm to busy in awe of the speed and very focused on the bluring terrain.

 

So I researched for 2 hrs and like my dad said I could find any opinion I wanted on the internet!  So I have lots of conflicting info

  1. Its normal for Wiseco ie this knock
  2. use Race Gas
  3. use octane boost
  4. use toluene in gas
  5. lean jetting

I'm new to bike building but  in the last year did 7-bottom ends, and been through 20 bikes, all ended in great success (so far but of course there were lots of mistakes along the way...).  I read nearly every day but I still need to learn a ton!  (yes valves are adjusted and I am all to aware that these 4-strokes are noisy machines an always feel like a bucket of bolts under you) 

 

My fears are telling me its the crank, but it does not make sense, my instincts are telling me to use higher octane gas, but its not a ping, its like a rattle sound, that is in perfect tune with the enging rpm.  Its running a 42 pilot at 32 F and 2400 feet of elevation, with high humidity.  Stock needle and clip posn, 170 main

 

Thanks Guys for reading, sorry for all the detail

Edited by bikedad1

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Knocking is somewhat normal with HC pistons. Just be sure it's not excessive. Stay away from octane boosters and you probably don't need race gas. It sounds like the bike runs really well, why mess with jetting? The only reason you should need to mess with jetting is if you ran race gas and it may need to go in either direction.

Edited by BDubb106
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I agree jetting seemed ok.  Needless Jetting just wastes valuable seat time in my opinion. 

 

I love that "just make sure its not excessive"  At least I have a benchmark now, still don't know what excessive is but its there and its nice to know its not abnormal.  Too bad I didn't check my post 3 hours ago LOL!!!!  Read on.....

 

Well I checked the vales yesterday,  looks like two had changed clearance alot, one exhuast value was 0.1mm, spec is 0.2mm.  amazing since i checked it three times  (all at the same time, you know, rotated engine..check)  even started it and checked again, few days later.  So fully worred I had a valve issue I rippered it down for "FUN"

 

I checked valve radial runout, valve stem runout, valve stem delflection, etc.  they all, speced out great, cylinder speced out too, new piston, so no worries there.  It did appear that one of the shims had made and imprint on the valve retainer (not sure it it was there before).  Hard to believe it was me!!  At any rate, Its all going back together.  Better to be safe than sorry.  Finally broke down and bought a bore guage.  It used to take be at least 1/2 hour with the snap guages and mic.  Slick!!! Bore turned out nice and round and in spec.

 

Ya it was running fantastic, but man was the knock loud-ish.  I want to sell the bike and did not want someone to pay fair price for a gernade.  Guess I better get one more blast on it!  curious,  why no octane boost?  I also read that 13:1 was kinda of the threshold for more than pump gas.  Not that I feel a need to have it, I do not believe in wasting money on "snake oil".  Just new to the highperformance stuff and want to do it right if possible.  PS I also don't think Highperformance is what most of us (me in particularly) need.  Save that for real competition!

 

Thanks Bdub for responding!

Edited by bikedad1

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if im not mistaken the 2006 rmz450 had a manual timing chain adjuster. if the timing chain is loose sometimes it could slap and sound like a piston knock..just thinking out loud

Edited by Cur4Sanity
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good thinking.  Start simple, proceed to complex.     Ya its manual and its adjusted,  Loosen adjuster nut at TDC, let internal spring push on chain and then torque (that's what I did at any rate).  I thought is was piston slap, or valves, they are both checked.  Only thing now is crank but I really don't think that is it.  I have a used (good) crank (from and 07)  on hand but really don't want to play that game.  Wish I new what bdub meant by "excessive".  Hey BDub, your sounding like my manual LOl.  Seriously though if it gets worse that's going to be the time to worry (I think).

Edited by bikedad1

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I agree jetting seemed ok. Needless Jetting just wastes valuable seat time in my opinion.

I love that "just make sure its not excessive" At least I have a benchmark now, still don't know what excessive is but its there and its nice to know its not abnormal. Too bad I didn't check my post 3 hours ago LOL!!!! Read on.....

Well I checked the vales yesterday, looks like two had changed clearance alot, one exhuast value was 0.1mm, spec is 0.2mm. amazing since i checked it three times (all at the same time, you know, rotated engine..check) even started it and checked again, few days later. So fully worred I had a valve issue I rippered it down for "FUN"

I checked valve radial runout, valve stem runout, valve stem delflection, etc. they all, speced out great, cylinder speced out too, new piston, so no worries there. It did appear that one of the shims had made and imprint on the valve retainer (not sure it it was there before). Hard to believe it was me!! At any rate, Its all going back together. Better to be safe than sorry. Finally broke down and bought a bore guage. It used to take be at least 1/2 hour with the snap guages and mic. Slick!!! Bore turned out nice and round and in spec.

Ya it was running fantastic, but man was the knock loud-ish. I want to sell the bike and did not want someone to pay fair price for a gernade. Guess I better get one more blast on it! curious, why no octane boost? I also read that 13:1 was kinda of the threshold for more than pump gas. Not that I feel a need to have it, I do not believe in wasting money on "snake oil". Just new to the highperformance stuff and want to do it right if possible. PS I also don't think Highperformance is what most of us (me in particularly) need. Save that for real competition!

Thanks Bdub for responding!

That is probably the reason for the knocking. Your valves. My bike knocks slightly at start up with the HC piston but it can only be heard at idle and it goes away once fully warm. At least I don't notice it anymore.

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My 250 knocked really bad also with a 13.8:1 hcp. Your decompression lever may be making that nasty clacking sound.. I took that hcp out and installed a oem piston from wiseco and walla NO MORE NOISE

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This is exactly what I need to hear.  Confirms my suspicions re hc piston.  Valves clearly need to be right!!!. that needs to be solved first (funny how they moved).  I do know that it was not like any valve noise I ever heard, plus they were too tight.   Interestingly the valve that the decompressor works on was in spec nice call tho slowgs.  I ordered shims put new valve stem seals in, new gaskets on the way.  be back together on friday.  So seriously race gas is supposed to reduce knock right.  Why should I stay away from it or octane boost.  Just curious.

 

btw bike purrs on the stand, its when riding it gets loud. 

does this make anyone suspicious

one exhaust shim is 2.35mm the other side is 2.15mm.  I have not yet seen such a spread on other bikes, seats looked good, passed the leak test. 

 

What do you guys use to clean the seats and valves.

 

Cool stuff guys, really apreciate the advice

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Hc pistons put a lot of stress on motors in general. It's always a no brainer to stick with OEM. Nonetheless, race fuel does help with detonation, but keep in mind that race fuel can get expensive. If that noise you hearing is the decompression lever then race fuel won't clear that clacking sound.

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I love that lucas stuff, got a bottle on the shelf (sticky as hell) and yes indeed spray cleaned, blown dry and lubed.  Heads back together.  just need to remove one valve, it failed a leak test, probably a tiny piece of carbon or a fat fingerprint left behind giving me grief.  Barely leaked but I can try to make it better.  I Discovered a new trick for the leak test.  I have a big piece of plate glass.  I fill the intake and exhuast ports with a tiny bit of . beer--errr...I mean  keroseen put the head on the glass, wich overhangs the bench and then shine a light under neath and look for leakage.  I  used to do this the hard way.  Any comments on the big difference in shims between same valves (one exhaust 2.3 mm and the other one 2.15mm)?

 

I could not agree more re the piston.  Crank must take a beating, not to mention the extra heat.  I don't like to change things like that just for recreational riding.  I did not have a choice, it came with the bike, plus a stand. extra FMF pipe, old cams (perfect), extra new valve, new in box HC piston (extra).  Has larger rads, boysen water pump.  All for $1700

photo(1).JPG

Edited by bikedad1
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Well guys this semi sucks!  I was waiting for fresh gaskets to put it all back together and I got a buyer.  He said he does not like the fact it has and HC piston.  I told him to Ship me one of his choice and I would install it and sell him the bike. He agreed, He used my dealer account with Rockymountain ATV, and chose a new wiseco standard piston.  Its on the way as we speak.  That's a good enough down payment/commitment for me.  he's driving 6-hrs to pick it up next weekend.  I Never get to ride it again and close the loop on this important learning experience.  I do sincerely thank you guys for taking the time to help me out!!!

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To close the loop for all other readers, I speced out the valves and head, valve stem runout, radial runout, Valve stem deflection, could not measure seat width, My poor old eyes with glasses just not sure enough lol.  Prussion blue works like crap for me Clearly its me. .  Did a leak test (passed...again) At any rate pulled the 2-hr old piston, {pristine}...measured piston to cylinder gap (in spec.).  Butt...pin (new) did have a bit of ware, like a trace all round it.  hmm not surgically assembled?  No rocking of pin in Conrod small end (did not measure..should have),  hate snap guages!! 

So conclusion...knock not  from bad valves, likely not crank, but not sure, probably piston and 91 octain gas???

 

 

New owner buys bike, it starts like a dream for me many times, warm cold, stalled.  For him can't even start it warm in my garage haha.  At any rate has trouble starting it, runs into a barbwire fence with only 1-hr of riding time and majically  cant start it... number plate is damaged.  Gee whats behind that (wires)  and he wants me to fix it, like its my fault!!!  Ya time to swear LOL

Edited by bikedad1

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?   could have been, only takes 3-beers!  Found out the fence he hit was an electric one.

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good thinking. Start simple, proceed to complex. Ya its manual and its adjusted, Loosen adjuster nut at TDC, let internal spring push on chain and then torque (that's what I did at any rate). I thought is was piston slap, or valves, they are both checked. Only thing now is crank but I really don't think that is it. I have a used (good) crank (from and 07) on hand but really don't want to play that game. Wish I new what bdub meant by "excessive". Hey BDub, your sounding like my manual LOl. Seriously though if it gets worse that's going to be the time to worry (I think).

not the best adjustment of mcct. I put it at tdc, tighten (term used loosely) until a small amount of tension, then use kickstarter to rotate engine as you tighten more, you will find like 2 spots where it will have more slack then tdc, anyway, once you can rotate engine through and get no more slack back it out a quarter turn. Think of how an acct works, it springs out at any slack, so you want to mimic that for best results, too tight will wear guides but too loose willl cost a fortune.

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Thats interesting thanks.  From what I've remember the 2007 rmz has a ratched only, and no.lock nut per-say? .The 2006 RMZ450 is different, it has a sliding shaft that is pressured by a spring that is held fast by a lock nut.  Set it once and it stays in place.  For the 2006, , your method would take up a bit more slack.  But in the case of the ratchet type, would not a slow turn over of the engin, using the flywheel nut allow the chain to find its slackest point?  Of for that matter, perhaps under varying high speed load, the chain may yield enough slack to allow the ratchet to find the next tighter notch, naturally? 

 

one thing for sure boys and girls.  Do not rotate the engine with the tensioner untensioned or your chain will skip on the sprokets and you wil be retimming it again LOL.

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Thats interesting thanks. From what I've remember the 2007 rmz has a ratched only, and no.lock nut per-say? .The 2006 RMZ450 is different, it has a sliding shaft that is pressured by a spring that is held fast by a lock nut. Set it once and it stays in place. For the 2006, , your method would take up a bit more slack. But in the case of the ratchet type, would not a slow turn over of the engin, using the flywheel nut allow the chain to find its slackest point? Of for that matter, perhaps under varying high speed load, the chain may yield enough slack to allow the ratchet to find the next tighter notch, naturally?

one thing for sure boys and girls. Do not rotate the engine with the tensioner untensioned or your chain will skip on the sprokets and you wil be retimming it again LOL.

if it has a spring ratchet it is automatic and will take up slack by itself, which is why I do the manuals like I do, it mimics a auto adjustment. Timing chain guide in bottom shoe behind flywheel? That could make a noise if it slips out during cylinder installation.... I have a 13.5:1 je, better because of skirt width, but I dont have a knock on 93. Richen your pilot and see if it helps maybe, but I think any radial play on crank is bad and would swap that out, thats where I would start.

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Thanks Honda man. I sold the bike, after the new owner wanted a "nomal" piston installed, so I did that, during which time I checked the valves again, bought v blocks and checked stem run out, etc.  All was fine.  REmeber previous "builder" had the cam timmng wrong, it would not start and the exhaust valves had just touched the piston crown. the new owner had hit  an electric barbed wire fence (damaging the number plate, clutch cable, etc) and it would not start.  I talked him through the fix, turned out a piece of aluminum from somewhere had broke off, or some thing and bent the exciter coil so no spark.  What a gong show (he did not care to try to find the source of the aluminum piece so I did not push it.  At any rate is was really hard working with the guy, cuase he said it would not start after a small spill.  After many conversations, I kept finding out details that he kept hiding.  At one point he could not get the shift lever on and beat it with a hammer and it would not shift anymore.  There is more to the story and the follies that followed, but he was a young guy that seemed keen and I think he learned alont from me and may end up as a pretty good bike fixer.  Remided me of myself when I was 20 (back in the 80's).  Bit of a wrench ape, but desire and experiece tempers that tendency.    Last I heard it was over heating (but he had been riding it alot so I think my work was good).  Hey they do that if you Idle them for 2 mins or so.... its a race bike and needs to be moving and rider needs to worry about riding slow in deep sand or tight woods.    Really not sure of the cause of the knock since I never did ride it after the new piston and the recheck of the top end.  However, I strongly suspect now that the crank (big end or small end) could have been the culprit (as you stated).  But I'm not sure since the bike was so clean I never did check the crank small end.  I hate using snap guages since it takes me quite a few "readings" to get consistent values.  Lesson learned!!!.  Ive done 8 bottom ends in the last year, kinda new to serious engine work, and I am learning so much.   I even answered and add from a guy who wanted a complete engine rebuild (kx250) and was willing to pay.  He was a heavy duty mechanic and lacked tools and confidence to work on small engines.  We did it together (I did not charge him).  The leak down test went for 12 mins and he lost maybee 0.5 psi.  He is really happy and his bike is running great. 

 

I really want to thank you and others on TT for the fantastic feed back, and your time and effort in helping fellow riders.  My latest project is a 2002 cr250.  Compression is 180, but turns out the guy was running 60:1 and 70:1 mixtures (found that out after the fact LOL)  the bike is jetted real lean on the main 340 vs 380-stock, and rich (one clip posn on the needle), and the piolet is also leaned one number.  At any rate I am commited to doing this stuff right and enjoy wrenching almost as much as riding (an do I ever love riding)  There is no way I could have done this easily 25-years ago with out the internet and peoply like you guys.  So once again.  Thankyou all so much.  BTW Hondaman.  Hondas are still my favorite bikes!!!

Edited by bikedad1
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