Author Topic: CB400f aftermarket piston kit  (Read 4212 times)

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Offline 9toe

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CB400f aftermarket piston kit
« on: October 13, 2024, 07:30:42 PM »
Any recommendations for aftermarket piston kits for a ‘75 CB400F pistons? I have seen some from Cruz in Images, 4 into 1 and some on eBay. My stock honda piston are oval. Cylinder are true.

Offline Nurse Julie

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Re: CB400f aftermarket piston kit
« Reply #1 on: October 14, 2024, 01:06:21 AM »
Cruzinimage kits are excellent.
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Offline newday777

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Re: CB400f aftermarket piston kit
« Reply #2 on: October 14, 2024, 03:07:19 AM »
Any recommendations for aftermarket piston kits for a ‘75 CB400F pistons? I have seen some from Cruz in Images, 4 into 1 and some on eBay. My stock honda piston are oval. Cylinder are true.
Did you use a machinist quality bore mic to measure the bore of the cylinders to be sure they are not tapered, as they usually wear in to be? Always best to do a fresh bore up size by +.25 at minimum(1st oversize set). You say you have oval pistons, so get bigger pistons and rings sets with fresh bores to tight tolerance clearance that these baby Fours require. Hondaman says they need to be .0004"-.0008" piston clearance, not bigger piston clearance so you don't have burning oil from too big of piston clearance.
Cruzin Image comes highly recommended as quality piston sets.
4into1.com doesn't come highly recommended. Cheap Chinese parts are not good quality items.

Read through this project rebuild
http://forums.sohc4.net/index.php?topic=179579.75
« Last Edit: October 14, 2024, 03:12:10 AM by newday777 »
Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
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1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
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New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
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Online bryanj

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Re: CB400f aftermarket piston kit
« Reply #3 on: October 14, 2024, 08:22:13 AM »
How oval? Most piston are fractionaly bigger front to back than side to side, a lot of car piston are measurably "oval"
The advise for a rebore is good BUT  you must use a machinist who understands Honda motorcycles plus recently i have found the 500/550 will not "clean" at 0.25mm due to barrelling of the liners
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline HondaMan

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Re: CB400f aftermarket piston kit
« Reply #4 on: October 14, 2024, 07:50:13 PM »
Cruzinimage kits are excellent.

I second that motion.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

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Offline 9toe

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Re: CB400f aftermarket piston kit
« Reply #5 on: October 15, 2024, 09:19:02 PM »
Cruising piston kits, got it and thanks. I will post some pics of the pistons. Cylinder to piston clearance is .0004 - .0008, that is a tight tolerance.