radiator cap bar/psi rating

got2dv8

After doing some maintenance and removing panels, I noticed some coolant spray on the rh side fairing. Looks like my radiator cap is giving up the ghost. Mine is rated 0.9bar which is only 13psi. Sourcing some replacements (thanks to Mr. R's post on using Honda) I have found many with different pressures. So, do I want to keep as close to oem pressure as possible... or can I go up in pressure? The average seems to be 1.6bar 23psi. What is that doing to my bike? I assume this would increase my coolant temperature. Would the higher pressure help or hurt?

I think the cap is the same as the KLR650 but I cannot directly confirm (anybody have a KLR?). If so I have found a nice stainless replacement with the standard 0.9bar rating.

Robert

Lawson SP3

Going up will (obviously) raise the pressure within the system before it vents. This raises the boiling point of the coolant as well. Both points are beneficial in most instances. If your hoses are OE and old, I'd not do it as they may not take the 'abuse'. If new or any of the silicone stuff, no sweat. One could argue the head gaskets might not withstand the extra and that could be valid. I can't say.

Side note: when I worked on the Indycars they ran much higher. Iirc, Honda used 18 and Cosworth used 20 (psi) and in both cases, we pressurized the systems after warming them up. Warm them up fully with the systems open and full up, shut off, drain off a measured amount for head space, cap them, pressurize. Ready for the day.

brad black

cooling systems are a real weakest link thing. fix one fault, the next weak link shits itself. i'd be wary of going up in pressure for that reason.

make sure the rubber under the cap is sitting correctly, etc. i'd try something from a fiat, alfa, etc, if you have a knowledgable supplier at hand.

Mr.R

The pattern CRF 250 Honda cap (fitted to my 851/916cc bike) is rated at 1.1bar, cost me around £1O inc' postage from E-bay, satisfied two of my personal bike fetish's as in it's S/steel so it won't rust/corrode and it's lighter in weight than the OEM item.
Been in use now for thousands of miles and over a year without any problems...RESULT!

If it ain't broke don't fix it, 1.1bar works OK for any road going (not sure what the Corse bikes used) 851/888, even those tuned to kick out close to 130rwbhp.

Steve R

duc904red

Only two fetishes?
Are you sure😉

got2dv8

The seller that I found for the klr cap is the same guy who sells the crf caps. In fact it's the same cap. So, thanks again and I'll be sticking with 0.9bar. Here is the seller.

Robert

Mr.R

duc904red wroteOnly two fetishes? Are you sure😉

😁 I didn't say how many I'd got, just that the rad cap satisfied two of them chap. 😝

Robert/Chaps,
That's the kiddy it's an exact copy of the one fitted to my '91 851 except it's lighter and in S/steel.
The OEM cap on my '92 851 didn't have the two ears/lugs to fit or remove it, but the pattern one was still lighter than that one.

Steve R

got2dv8

Cap not compatible w/ 851

I just received my stainless cap and thought I'd throw it on. But no! The cap I purchased is not compatible with my 851 radiator. It's lower gasket and backing plate are larger than the actual opening in the radiator AND the travel is also too short. I am still looking for a replacement cap to fit the 851.

Robert
ps. I ended up removing and flipping the large diameter rubber gasket on my oem cap, which should buy me some time. Replacement of said rubber gasket would solve my problem.

ducati dad

Is this any good? http://www.ebay.de/itm/Ducati-Kuhler...item589be82bf9

Mr.R

Sorry about that Robert.
The pattern CRF one that I've got fits 2 of my 851/888 rads the curved '92 and Corse.
I've just checked it and it doesn't fit my '91 rad that has a 0.9bar cap.
I've just stumbled over the box it came in it's made by "fah-ler" for Asian & Japanese cars, it's rated at 1.1 bar as is the OEM cap from my '92 851 and my Corse rads.

Steve R

got2dv8

Mr.R wrote

Not your fault Steve. I only assumed. At least now we know that the caps from 89-91 are different than the 92+. Plus, I read a thread by someone from UK who had an SP2 and noted they were different also.

Robert

DeltaT

bit of a resurrection but does anyone know which cap DOES fit an '89 bike?

Jasper

Mr.R wroteThe pattern CRF 250 Honda cap (fitted to my 851/916cc bike) is rated at 1.1bar, cost me around £1O inc' postage from E-bay, satisfied two of my personal bike fetish's as in it's S/steel so it won't rust/corrode and it's lighter in weight than the OEM item. Been in use now for thousands of miles and over a year without any problems...RESULT! If it ain't broke don't fix it, 1.1bar works OK for any road going (not sure what the Corse bikes used) 851/888, even those tuned to kick out close to 130rwbhp. Steve R

I have the same cap on my SP5.

got2Lev8

DeltaT wrotebit of a resurrection but does anyone know which cap DOES fit an '89 bike?

This cap fits my '90 and should fit the '89. Part no. 800055063
The later models used a different one.

Robert

DeltaT

ahh that looks more like it, thanks. Now to find somewhere that has one in stock...

DeltaT

...don't suppose you bought two did you? 😄

All I'm getting is out of stock, discontinued, no replacement or updated part no.

There must be something else out there the same size.