Author Topic: IMD Piston kits compared with CruzinImage Piston kits  (Read 794 times)

0 Members and 1 Guest are viewing this topic.

Offline Cooper

  • Club Member
  • Back Lane Scratcher
  • Posts: 53
IMD Piston kits compared with CruzinImage Piston kits
« on: December 20, 2019, 03:58:17 PM »
I recently bought RD350 for both cylinders +1.50 piston kits from CruzinImage and +1.25 piston kits from IMD. The reason for the different sizes is that the CruzinImage kits are offered only at 0.50mm intervals, the IMD at 0.25mm. I offer no opinion other than to say that neither taste of cheese.

CruzinImage
Listed as for 1973-1975 models only. I placed my order on the CruzinImage Japan website and received later the same day a courteous Email from Mitsuo thanking me for the order and providing a Japan Post tracking number. The cost to me including shipping to me here in London and taxes was $60 USD, paid with PayPal which turned out to be £48.41.
The package was delivered on the 5th day after placing the order. There were no additional import duties or taxes applied. They arrived well packed in albeit unbranded packaging with rings, gudgeon pins and circlips in separate bags
The pistons themselves are bare alloy without any kind of coating. The crowns are textured. They have exhaust side cut-outs in the skirts and the castings identified inside as 1A100. Measured with a micrometer at 90 degrees to the pin they are 0.0072" less than nominal immediately below the rings and 0.0017" less than nominal at the foot of the skirt. Weight including rings, pin and clips is 257 grams.

IMD
These are of the 4LO LC variety Listed as for RD350 and RD350LC. I ordered these via Ebay at a delivered cost of £63.89, taking advantage of a -15% Black Friday offer. These were delivered on the 3rd day after placing the order. They were very nicely packaged in a branded carton with rings and pins in place on the pistons. Empty ring cartons are included, branded TKRJ Industry Made In Japan. The pistons have what seems like an OEM type coating. The crowns are smooth. The castings are identified inside as TKR-4LO JAPAN which seems to fit with the rings carton. Immediately below the rings they are 0.0139" less than nominal and at the foot of the skirt 0.0021" less than nominal. Weight including rings, pin and clips is 266 grams.

« Last Edit: January 02, 2020, 10:02:04 PM by Cooper »

Offline 5port

  • Club Member
  • Port Hacker
  • Posts: 8805
Re: IMD Piston kits compared with CruzinImage Piston kits
« Reply #1 on: December 20, 2019, 07:47:02 PM »
Good post Russ.  The TKRJ have a flash coat of tin, similar to OE.  It has some effect on initial running-in.  You can see the cruzinimage have the port cut-out in the front skirt.  That is correct for the 1A1  and 1A3 C/D.  The 2R9 400E/F did not have that.  However, if anyone is choosing to use the Cruzinimage piston in a 350 aircooled, they should find that the cut out remains below the bottom of the exhaust port floor at TDC and so it is not a factor for the 350.
The TKRJ is a 350LC pattern and, as you found, has a different profile.  That said, it is the correct overall shape with no front skirt cut out and that detail suits the 2R9 400E/F.  However, the LC optimised profile is not the same as the 2R9 aircooled.   ???

5port   
5port

Offline Cooper

  • Club Member
  • Back Lane Scratcher
  • Posts: 53
Re: IMD Piston kits compared with CruzinImage Piston kits
« Reply #2 on: January 02, 2020, 10:25:56 PM »
Suggesting that the LC profile pistons are designed to run (somewhat unintuitively, to me at least), at a higher temperature than the air-cooled profile assuming a similar mass at the crown. I wonder if the extra clearance of an LC piston in an AC cylinder results in faster wear and perhaps rewards piston renewal between rebores, something I'm toying with as my bores seem to measure up favourably although they do show some scuffing.
« Last Edit: January 02, 2020, 10:35:53 PM by Cooper »

Offline betty foRD

  • Peter
  • Club Member
  • Port Hacker
  • Posts: 2426
  • Age: 57
  • Location: Faringdon (Oxon)
Re: IMD Piston kits compared with CruzinImage Piston kits
« Reply #3 on: January 03, 2020, 12:25:54 AM »
Suggesting that the LC profile pistons are designed to run (somewhat unintuitively, to me at least), at a higher temperature than the air-cooled profile assuming a similar mass at the crown. I wonder if the extra clearance of an LC piston in an AC cylinder results in faster wear and perhaps rewards piston renewal between rebores, something I'm toying with as my bores seem to measure up favourably although they do show some scuffing.

Don’t follow why you think the LC piston measurements imply it will be running hotter...
The water cooled LC bore expands less than the Aircooled bore, but piston expansion even with a cooler piston results in larger differential movement on a LC setup. Consequently the LC needs a larger cold running clearance.
Rev 'em till they rattle

Offline Cooper

  • Club Member
  • Back Lane Scratcher
  • Posts: 53
Re: IMD Piston kits compared with CruzinImage Piston kits
« Reply #4 on: January 03, 2020, 12:55:42 AM »
Betty In any event, don’t get the impression that I’m doubting the veracity of what you say but is it not the case that a cold piston with a proportionately smaller diameter at the high mass crown end to at the low mass skirt end requires a greater increase in temperature for the top to expand to the diameter of the bottom than that of a piston with a crown diameter closer to that of its skirt? ;) I fear that I may be blind to the wood because I’m looking at all the trees.
« Last Edit: January 03, 2020, 12:57:34 AM by Cooper »

Offline 5port

  • Club Member
  • Port Hacker
  • Posts: 8805
Re: IMD Piston kits compared with CruzinImage Piston kits
« Reply #5 on: January 03, 2020, 08:55:19 AM »
I wonder if the extra clearance of an LC piston in an AC cylinder results in faster wear and perhaps rewards piston renewal between rebores, something I'm toying with as my bores seem to measure up favourably although they do show some scuffing.

Hi Cooper,
The likely benefit of fitting new pistons in a used bore can be judged by accurately measuring the bore profile and comparing to an accurate original profile then comparing this to the same measurements for the new and worn piston.  This is essentially similar to measuring ring wear, but much more difficult .  However, few of us are able to measure to the accuracy required and, even fewer record this for comparison.  Also, installed ring wear (gaps) are specified much better than piston wear and some of us do measure ring gaps at decoke and replace rings.  In fact, piston wear limit is almost never specified by Yamaha!  The specification given is purely the front/rear skirt clearance at 10mm from the bottom of the liner and skirt and, is just the new-fit tolerance, not the wear limit.  I have found some reference to a 0.1mm (4thou inch) limit for the skirt wear but, my experience with the aircooled is that piston rattle is very noticable by 2.5thou inch of skirt/liner clearance.  I think that most owners judge piston/bore wear by the noise and some by compression or performance.
Please remember I am talking about standard aircooled engines with standard aircooled pistons.   Cheers

5port 
   
5port

Offline Cooper

  • Club Member
  • Back Lane Scratcher
  • Posts: 53
Re: IMD Piston kits compared with CruzinImage Piston kits
« Reply #6 on: January 03, 2020, 12:52:26 PM »
Thanks 5port. With the benefit of your advice I'm going to revisit my bore measurements, measure the worn pistons and compare both to what I think I've learned about a CruzinImage AC piston profile.

Offline betty foRD

  • Peter
  • Club Member
  • Port Hacker
  • Posts: 2426
  • Age: 57
  • Location: Faringdon (Oxon)
Re: IMD Piston kits compared with CruzinImage Piston kits
« Reply #7 on: January 03, 2020, 11:57:58 PM »
Betty In any event, don’t get the impression that I’m doubting the veracity of what you say but is it not the case that a cold piston with a proportionately smaller diameter at the high mass crown end to at the low mass skirt end requires a greater increase in temperature for the top to expand to the diameter of the bottom than that of a piston with a crown diameter closer to that of its skirt? ;) I fear that I may be blind to the wood because I’m looking at all the trees.

Yes, I think that’s correct. (I’m Not referring to  the wood and the trees) ..  In an LC even though the piston will be cooler overall for the same load conditions there is a much larger temperature gradient down the piston as the business end is cooking whilst the bottom of the skirt is in contact with a relatively cool liner and the exhaust port is water cooled.  The AC in bore will be quite different in that respect.
Rev 'em till they rattle