KDXRIDER.NET

Can anyone tell me the thread size for the radiator drain vent bolt (upper), Kawasaki P/N 92002-1682 as used on H series radiators?

I know the pitch is 1.25 mm, but the OD of the bolt, measured across the threads is .457 " which does not come out to any even millimeter dimension. I'm thinking this might be 12 mm X 1.25 but don't have a bolt or tap to see how it threads into the radiator tapping.

I want to buy or make an adaptor for a Trail Tech coolant temperature sensor that will thread directly into the radiator, rather than cut my hose and splice in the Trail Tech adaptor that came with my computer kit.

Thanks for your reply.

12 mm is 0.47 in , .457 is around 11.7 mm so most likely a m12

You are correct!

A check with OEM bolt in new hardware store nut confirms thread size is 12 x 1.25.

THANKS!

Now to find an adaptor so I can thread my Trail Tech heat sensor lead directly into my radiator. Trail Tech lists 12 x 1.5 adaptors, but not 12 x 1.25.

I would consider making one, but Trail Tech's sensor lead is threaded 1/8-28 BSPP (British Standard Parallel Pipe) which is a real oddball for us here in the USA.

Looks like I may have to cut the radiator hose after all and splice in the Trail Tech fitting. I was hoping to avoid that, but.....

post a pic of your solution if you can.
as i am about to buy a trail tech too.
thanks mark

I have a message in to Trail Tech now asking if they can supply an adaptor threaded M12 x 1.25 but no answer yet.

Have to check their site, but I'm quite certain they offer larger adaptors like 14 mm & larger with 1/8 -28 BSPP tapping.

I am thinking now if TT can't supply M12 X 1.25 adaptor, I will buy one of their larger adaptors and turn down and thread the OD to M12 X 1.25 threads.

Whats wrong with the splice-in sensor style? No real good place to do the splice? Just curious... I have this style for my dualsport, but haven't put it on yet. My biggest concern was finding a decent place to put it. Right on top of the head looked like the best place to me, fitment-wise.

Yeah, others on this site have put their sensors up top between the 2 radiators too, and I thought about doing that as well.

I'm just kind of particular about stuff like that. If there's a plug on top of the radiator that has no useful purpose, to me it's obvious that's where the temperature sensor should go.

Besides, I don't want to cut my radiator hose unless I have to. Two more places for a possible leak.

Completely understandable.

Think you could drill a hole through that plastic plug that's in there now to run the sensor through and epoxy the hole back up to seal it?

Actually...when I was talking about a location, I meant right next to the coolant nipple in the head. I didn't even think of between the radiators up top. I like that idea even better. Thanks!

And for the leaks with the splices... I wouldn't be too concerned. I had to splice a KDX hose to a KX hose when I was putting my hybrid together. I couldn't find any barbed fittings that were the exact length and diameter that I needed. I ended up picking up a PEX fitting (those plastic water lines for your house) from Lowes and am using that to splice the two hoses together. Its working great with a clamp on either side. I dunno, its relatively low pressure, just trying to say its not that bad of an option if its your only choice.

Well, being a machinist of sorts having a lathe, drill press, and milling machine, I would want to do it in a way I consider proper, which is to use suitable metal to make the adaptor. I would rather not use epoxy if I can avoid it.

I just got a reply from Trail Tech saying they do not offer an adaptor with M12 x 1.25 threads. The person replying said he has a KLX 300 with the same issue.

He also said they have no plans to offer this size adaptor.

So it looks like I have to switch to plan B, buying a larger adaptor, turning it down to 12 mm and threading it with 1.25 mm pitch threads.

If it wasn't for the oddball 1/8-28 BSPP threads on the sensor lead, I would have it made by now.

How about an M12x1.25 to barbed fitting? Then you could insert the fitting in the radiator, and fix the sensor to it with a short piece of tubing. That way you don't splice into your cooling lines, and it's completely reversible if you ever want to take it out

Hmmm..., Interesting idea. I'll have to give that some thought.

If I'm understanding your idea, I'm thinking maybe with the sensor some distance away from the coolant flow, there may be a temperature loss, and the reading might be lower than actual coolant temperature.

I heard back again from Trail Tech, and they offered a few suggestions for adaptors that could be turned down and rethreaded to fit my radiator.

Got to think on this some more.

If I had access to a drill press/milling machine, then an aluminum bung plug (like this) and a BSPP Tap (BSPP Tap), and call it a day.

Right! Thank you for your research. The key issue is that 1/8-28 BSPP tap.

I've been doing machine work for decades, and that includes an interest in model engineering as done primarily in the UK where special Whitworth, BA, and Model Engineering thread sizes are used, and I'd never heard of a 1/8-28 BSPP thread size.

After looking, I did find it in Machinery's Handbook, and a Google search also provided information. Why Trail Tech chose that thread size over a common 1/8-27 NPT thread I'll never know, but it is what is.

One thing is certain, unless I need to make more than one of these adaptors for a Trail Tech heat sensor, I would never have a need for a 1/8-28 BSPP tap again.

So, as of right now, it appears the most cost effective solution is to buy a larger Trail Tech adaptor and turn down and thread the OD to M12 X 1.25 thread size.

Trail Tech suggested their VA 16150 or VA 18150 adaptors might be suitable for this modification.