Spyvsspy

Replacement piston for big bore kit

32 posts in this topic

Hello all...I am looking for some direction.  I received a complete but used cylinder works bbk(94mm).  5k miles on it. I am going to have the piston and cylinder checked out at a buddy's machine shop.  There was contact with a valve.  It is a vertex piston 93.97mm.  If I can't reuse piston I wanted to order a JE piston because it says they can handle higher compression and i plan on using e model base gasket.  Also, will the cometic gasket kit work on the cylinder works head? Any advice on a good write up for doing the installation myself?  Any tips or advice to help me out?  I already have a fcr39mx with a full yoshi rs2 which I installed a few months ago.

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That piston is junk. It smacked the valves (backwards?). I would be suspicious of the cylinder as well.

 

Cylinder Works cylinders are matched to the appropriate Vertex piston as they are available in 4 sizes,(A thru D) You can use a Vertex piston and run single layer gasket without a problem.

 

Cylinder Works kits are delivered (at least mine was) with Cometic gaskets

 

 

 

 

 

 

 

 

 

 

 

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17 minutes ago, ohiodrz400sm said:

That piston is junk. It smacked the valves (backwards?). I would be suspicious of the cylinder as well.

 

Cylinder Works cylinders are matched to the appropriate Vertex piston as they are available in 4 sizes,(A thru D) You can use a Vertex piston and run single layer gasket without a problem.

 

Cylinder Works kits are delivered (at least mine was) with Cometic gaskets

 

 

 

 

 

 

 

 

 

 

 

I was 95% sure I was going to replace the piston...I've heard that you can reuse pistons and cylinders as long as they check out.  I will be taking it to a machine shop to have it inspected.  I got it for free so if I am out a new piston and gaskets I feel I am ahead.  It is a "C" piston.  Says 93.97 C on it...so no JE compatibility?

Edited by Spyvsspy
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https://www.amazon.com/Vertex-23533C-Big-Bore-Piston/dp/B0031BUKQE

If this is the correct Vertex piston i need to replace the damaged one then this is a damn good price.  I have seen the vertex 23533C pistons on the cylinder works site for $200+...anybody have feedback on this?

https://www.amazon.com/gp/aw/d/B000GTV2GQ/ref=ox_sc_act_image_1?smid=AY6B10HJNSJYH&psc=1

also found the cometic gasket kit part #: c7979.  It says it fits the ltz400 with the 94mm kit.  If these two items in amazon are legit then this is the shiznits.

 

Edited by Spyvsspy

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Someone screwed up with the listing and probably sold a pile quickly which alarmed them , so the price was changed. I've found anytime you see a ridiculously low price for something , buy it immediately before they catch it , sometimes it only takes an hour or 2 till the word gets out and there's a rash of sales.

As for the piston, you can use any of the forged pistons in that motor , they'll all handle it fine. Key is to know the exact diameter of the cylinder and get the piston that is withing the clearance spec . I used a different piston than what came with my cylinder , just had the company pick out a piston the was the size I spec'd out . You can always send the piston to be coated to close up some clearances . Don't forget to verify ring endgaps !!

 

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I just got back from the shop.  I was suprised to hear from the machinist that I can reuse all the components down to the rings and circlips!  He advised to sand and smooth the areas that were hit by the valve but he said that the contact was light enough not to damage the piston.  

Im going to clean everything afterwards and install it myself when my next oil change is due in about 2500 miles.  I still need to order the gasket kit which is only $34 on amazon - C7979!  That means I'll only be out $45 for the kit!

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I Was advised to do a light hone with a ball hone and drill.  I thought that nikasil coated cylinders don't require any honing?  Advice?

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The light hone is to put some of the cross hatches back in for seating the rings , it is ideal . I use ball hones to quickly scuff up the surfaces , 320grit usually  , depending on mfg.

 

 

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48 minutes ago, Spyvsspy said:

I Was advised to do a light hone with a ball hone and drill.  I thought that nikasil coated cylinders don't require any honing?  Advice?

Yes, I also like to do what JJ says, but be prepared, It may smoke out the tail pipe for the first 2 or 3 start ups until the rings are fully seated.

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Ball hone is best; I have used a straight hone as well for only 3-4 slow turns.  Like stated, all you want is to establish cross-hatch for ring seating to take place. Some guys "run it like they stole it", others just run up and down the RPM range with a light load for 30 min.  Read and choose which way you want to break it in.  Either way, change oil after 30 min of run time and you'll be GTG.

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I just got back from the shop.  I was suprised to hear from the machinist that I can reuse all the components down to the rings and circlips!  He advised to sand and smooth the areas that were hit by the valve but he said that the contact was light enough not to damage the piston.  
Im going to clean everything afterwards and install it myself when my next oil change is due in about 2500 miles.  I still need to order the gasket kit which is only $34 on amazon - C7979!  That means I'll only be out $45 for the kit!


Do yourself a favor and don't reuse the circlips. If that piston fails you'll wish like hell you spent $230 on a new unit.

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2 hours ago, Spyvsspy said:

 

.... when my next oil change is due in about 2500 miles. 

surely this is a typo?

its only 2 qts of oil (and hopefully a filter) most DRZ owners shoot for 1000 or less miles between oil changes....

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14 minutes ago, RetroRanger said:

surely this is a typo?

its only 2 qts of oil (and hopefully a filter) most DRZ owners shoot for 1000 or less miles between oil changes....

No typo...the factory calls for 3.5k oil change intervals.  I thought 2.5 was overkill

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That's a pretty long interval, it's pretty much agreed up the manual was wrong in that respect. I change mine every 1k. 1,250 mi feels like too much for me. My full synth is definitely black at 1k.

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50 minutes ago, HansLanda said:

That's a pretty long interval, it's pretty much agreed up the manual was wrong in that respect. I change mine every 1k. 1,250 mi feels like too much for me. My full synth is definitely black at 1k.

I regularly check my oil levels.  More important is the consistency of the oil.  As it breaks down it gets thicker.  If you change oil and you notice it black that is just a product of your internal temperatures.  If you see metal flakes with the black then you are in trouble.  I switched to conventional oil because I read that it quiets down motor noise.  So far it has...I will be pulling oil at 2500 and doing a UOA to see if everything looks good.  

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I regularly check my oil levels.  More important is the consistency of the oil.  As it breaks down it gets thicker.  If you change oil and you notice it black that is just a product of your internal temperatures.  If you see metal flakes with the black then you are in trouble.  I switched to conventional oil because I read that it quiets down motor noise.  So far it has...I will be pulling oil at 2500 and doing a UOA to see if everything looks good.  


OIL THREAD!!!!!!!!!!!!!!!

Actually the oil gets thinner as the molecular chains are broken down by the shearing forces in the gear box.
Motorcycles are much harder on oil then automobiles.

I'm interested in seeing results from 2500 miles. Others have posted results that show 40 weight losing viscosity around the 1k mark.
https://thumpertalk.com/index.php?/topic/377246-DRZ400-SM-Oil-Analysis
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yahhhhh oil thread.

do what you want, but most people here will tell you 1000mi is a good time to change. with the trans. and clutch the oil gets a lot of aluminum in the oil. long term reliability will be enhanced with frequent changes.

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26 minutes ago, bucket list said:

yahhhhh oil thread.

do what you want, but most people here will tell you 1000mi is a good time to change. with the trans. and clutch the oil gets a lot of aluminum in the oil. long term reliability will be enhanced with frequent changes.

I'll do a UOA at 1k and see how it looks

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