Coolant Plug in Underside of Cylinder?

[Kawibunga]

Final check last night. Can confirm. These are absolutely a 19 TPI 3/8" BSP threads. Not a standard 18 TPI 3/8" NPT or a metric 1.5X16mm thread. Which is all just crazy to me and makes no sense. But I checked everything with my pitch gauges last night. The replacement plug worked as it was a bit longer therefore the taper was longer and it had the length to it to allow it to tighten up and seal. The stock plug is shorter and wouldn't tighten up enough to seal before I was flush and out of length..........

[smelonas]

Glad someone went through the process of figuring this out and then posting it, with a replacement part! Always amazes me how even on these old ass bikes we can find a 'new' part in some nook and cranny area like this.

[KDXGarage]

THANK YOU for the information.

[Chuck78]

Was just doing a tune up on a 18 hp Briggs and Stratton V twin yesterday. The oil drain bolt was very similar looking to the ones on our cylinders. I doubt it will work but might be worth checking.

So this Amazon link for a Briggs & Stratton 3/8" BSP plug 10-pack is the one we need?

Did you have to buy a 10-pack? Care to sell a few of those for nearly what you paid for all 10, if so?

[JZ05220r]

Was just doing a tune up on a 18 hp Briggs and Stratton V twin yesterday. The oil drain bolt was very similar looking to the ones on our cylinders. I doubt it will work but might be worth checking.

So this Amazon link for a Briggs & Stratton 3/8" BSP plug 10-pack is the one we need?

Did you have to buy a 10-pack? Care to sell a few of those for nearly what you paid for all 10, if so?

Hey Charlie, I didn’t order any. Just suggested that it MAY work, and left a link. I have an extra aftermarket one. It is not the correct pitch but it will seal if your interested.

[Chuck78]

It really does look to me like a 3/8" BPST thread, a few more measurements will confirm.

On the weekend I installed the plugs I ordered off amazon. These plugs were slightly longer, seemed to be the identical thread on initial measurement (but still confirming that 100%) with it being longer. I got it to tighten up way nicer while threading in. I also used good PTFE tape instead, felt really nice threading in........... and bingo, got a good seal, no leaks at temp!

Here's the new plug vs original, you can see it's a wee bit taller

PXL_20231008_162956388.jpg

Here it's installed, nice an tight (not over tight) and sitting slightly proud. Threaded in nice. After the fact I will now take a few more measurements and report back. But these worked great. Here's what I ordered.......
PXL_20231008_163006433.MP.jpg


They call them both NPT and BSSP which is obviously wrong, you can't be both, NPT is slightly larger OD and 18 TPI while BPST 19 TPI and slightly smaller OD.......... it still makes no sense to me that it's not a metric thread, but that's what I've found out so far. More to come once I take some final measurements........

EDIT - it appears that the amazon versions are 3/8" BSPP, not 3/8" BSPT. A search on scamazon for 3/8 BPST brings up only BSPP results (straight thread, BSPT is tapered thread).

[Kawibunga]

Yeah, I have no idea of those Briggs & Stratton JZ0522r suggested would work, might be just regular NPT, but mine definitely did and I do have spares. 3/8 BSPT 19TPI as stated. Now for shipping them out, got no issues sticking some in the mail for ya Chuck78, just have no idea the postage from here in Canada to where you are in the US........... but yeah, I don't need 9 spares on my shelf! :)

[Slick_Nick]

Yeah, I have no idea of those Briggs & Stratton JZ0522r suggested would work, might be just regular NPT, but mine definitely did and I do have spares. 3/8 BSPT 19TPI as stated. Now for shipping them out, got no issues sticking some in the mail for ya Chuck78, just have no idea the postage from here in Canada to where you are in the US........... but yeah, I don't need 9 spares on my shelf! :)

Maybe I missed it, but where did you manage to pick some up locally? I use Blackfoot Industrial for a lot of my hardware, they seem to have lots of oddball sizes, but this is REALLY oddball!

[Kawibunga]

Took a shot at Amazon, the product was mislabeled calling it both NPT & BSPT - turns out is was the 19TPI BPST version. The bigger challenge was pickup up a 19TPI pitch gauge!............. but for fastener etc locally I'm typically Greggs, Bolt Supply or Calgary Fasteners - but will have to check out Blackfoot Industrial, thanks for the heads up!

[Slick_Nick]

The guys at Blackfoot Industrial are great, and their stuff is about half the price of the "big box" store across the street (Calgary Fastener and Tool)

I wanted to send you a PM, but I see that you don't have that option enabled. You're the only local guy I know here with a KDX, what are you running for suspension? The factory stuff? If you're interested in some fancy upgrades let me know, I've got some bolt on stuff taking up space in my shop that I'm looking to get rid of.

[Kawibunga]

Not sure what's going on, should be able to enable it but I get the error............. "You are not authorized to read private messages" but my boxes in the other tabs are all checked, no idea. Just fire me off an old fashioned note "rjgraf74 at that good ol goggle email dot com"........ in the mean time I'll see if I can sort out the PM function, would be handy!

[KDXGarage]

Hi. PMs are just for supporting members. You may want to type out your e-mail address in words, as the internet bots can harvest it and start spamming you.

[Kawibunga]

Hi. PMs are just for supporting members. You may want to type out your e-mail address in words, as the internet bots can harvest it and start spamming you.

Ahhhh, good to know KDXGarage - no problem supporting. Can it be a one time donation or does it have to be a regular monthly or yearly donation?

[Slick_Nick]

Hi. PMs are just for supporting members. You may want to type out your e-mail address in words, as the internet bots can harvest it and start spamming you.

Ahhhh, good to know KDXGarage - no problem supporting. Can it be a one time donation or does it have to be a regular monthly or yearly donation?

I sent you an email, should be buried in your junk folder somewhere I'm sure!

[Chuck78]

https://www.ebay.com/itm/224515867144

These appear to be the same stainless steel 3/8" BSPP pipe thread plugs listed in the Amazon link above, but shipped from China.
But are they tapered 3/8" BSPT?
Or are they straight thread 3/8" BSPP?
Both BSPP and BSPT are discussed here, and also referenced as just BSP.

I need to buy one to replace my missing plug that PowerSeal USA removed and lost when replating my cylinder...

[Tyl3r]

RE:CONFIRMED - I did not have a plug to measure and compare when I originally did this, but thanks to Kawibunga for the detective work and comparison to an original part, the correct thread spec for the plug is 3/8" BSPT (update 1/1/24)

CONFIRMED! The thread size for the coolant plug on the underside of the cylinder is most certainly M16x1.5. I tried a 3/8" NPT and it would start into the hole but stop. Here is a link to a plug if you need it, got mine from Belmetric, saw that Fastenal also sells them: https://belmetric.com/stainless-taper-m ... P16X1.5TSS

[Chuck78]

So are these tapered 3/8" BSPT?
Or are they straight thread 3/8" BSPP?
Both BSPP and BSPT are discussed here, and also referenced as just BSP.

[Tyl3r]

BSPT has a tapered thread and seals in the threads like an NPT. BSPP is parallel threads would require a shoulder with an O-ring to have a seal.

tapered-threads-vs-parallel-threads.jpg (53.7 KiB) Viewed 9961 times

[JZ05220r]

RE:CONFIRMED - I did not have a plug to measure and compare when I originally did this, but thanks to Kawibunga for the detective work and comparison to an original part, the correct thread spec for the plug is 3/8" BSPT (update 1/1/24)

CONFIRMED! The thread size for the coolant plug on the underside of the cylinder is most certainly M16x1.5. I tried a 3/8" NPT and it would start into the hole but stop. Here is a link to a plug if you need it, got mine from Belmetric, saw that Fastenal also sells them: https://belmetric.com/stainless-taper-m ... P16X1.5TSS

Did it bottom out flush like the standard plug or were their any differences with the fit in any way?

[Kawibunga]

Mine went in really nice, perfect fit, but slightly protruded when it tightened up compared to the stock plug. Posted a pic of it back in the thread. Certainly not enough to cause any issues though