2 STROKE WORLD .net

The 2-Stroke Garage => Turning Wrenches => Topic started by: Kawtriplefreak on January 08, 2026, 06:47:49 PM

Title: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 08, 2026, 06:47:49 PM
(https://i.postimg.cc/BvqkCTXP/20260108-170350.jpg) (https://postimg.cc/yDbL1Sh7)
My son paid for this and an LED headlight bulb for me for Christmas.  They both arrived today. The radiator was $69 shipped from Ebay. I haven't had any heating problems with the slightly oversized radiator installed but when I saw this one twice the size (42MM vs 19) I figured it might be good insurance when it gets hot outside.
(https://i.postimg.cc/C5H6DdSG/20260108-170403.jpg) (https://postimg.cc/zHvjYzLv)
Pure Chinesium no doubt. The fit is good, not perfect. The top pin only goes halfway into the rubber but it isn't moving once installed. The hose fitting for the hose that goes from the radiator to the head is angled slightly different and nearly strikes my cooling fan bracket so some finaggling will be required to complete the install.

Title: Re: Radiator Upgrade RZ421
Post by: 85RZwade on January 08, 2026, 09:33:23 PM
I have two of those radiators, and I am baffled as to how they can be (apparently) so well made and be so inexpensive. Waiting to hear your performance review.
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 10, 2026, 12:54:13 AM
I spent all afternoon redoing the cooling fan bracket. I made the 1st one and tightened everything down and didn't take the coolant reservoir I had removed to gain access into account. So back to the drawing board it was.
(https://i.postimg.cc/QtYgBKFK/20260109-163137.jpg) (https://postimg.cc/34p0VRC3)

Bracket #2 fits well and gives me good clearance. All that's left is installing the hose clamps and pour in some coolant.
Title: Re: Radiator Upgrade RZ421
Post by: rodneya on January 10, 2026, 11:54:05 AM
Quote from: 85RZwade on January 08, 2026, 09:33:23 PMI have two of those radiators, and I am baffled as to how they can be (apparently) so well made and be so inexpensive. Waiting to hear your performance review.

I had a LC version on my 421 and you are right to say that they are really cheap and quite well made. My bike still ran really hot in traffic in summer with the fan running constantly, so I ended up replacing it with a curved R6 rad which made a huge difference.
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 11, 2026, 01:22:57 AM
Radiator install complete. Filled with coolant. It held nearly 2 quarts. Squeezed the hoses and burped out quite a bit of air. Ran it up with the cap off and got some more air. No leaks noted. Put the cap on and it took about 8 minutes to reach 140 degrees. Let it cool and topped it off again
Next I turned my attention to fitting the factory radiator cover.
(https://i.postimg.cc/4NyzDr6c/20260110-164344.jpg) (https://postimg.cc/svFQSH0f)
I made a bracket to space it out properly and ended up putting a couple pieces of foam between the cover and the tank on the bottom to keep the cover from touching the fins. Then I used cable ties as before to secure the bottom to the factory cover rubbers on each side. I was concerned about the forks striking the cover at full lock but ended up with about 1/2 inch of clearence.
(https://i.postimg.cc/KcJWrhcM/20260110-164414.jpg) (https://postimg.cc/Hj83dKyY)
Thanks M in SC for the advice as always.

Title: Re: Radiator Upgrade RZ421
Post by: RDryan on January 11, 2026, 08:04:28 AM
Looks well done. Getting to be a well sorted highly modified bike you have as I live vicariously thru your posts of the Gray Ghost  :wave:

Getting back to what you said about not having any cooling issues. So when I see some of your ride videos they conjure up bike lust, wander lust at least for me. I figure living in a rural area like that the bike is always on the move and never stuck in traffic.

FWIW I acquired a similar kinda radiator on Ebay to repair my GSXR 1000. Gotta love it for the quality and value and ironically how can be a bad thing to increase the coolant capacity?
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 11, 2026, 09:44:41 AM
Thanks for the kind words. I have spent some time in traffic and we did have some 65 degree days here and no issues with the other radiator. The way it was explained to me is the thicker core can flow less air and exacerbate cooling issues instead of alleviating them. A lot of the guys in the UK with these conversions are running similar radiators with great success. We will see. M in SC please elaborate if I explained that wrong.
 
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 12, 2026, 12:12:39 AM
(https://i.postimg.cc/qB3mdPbL/20260111-165004.jpg) (https://postimg.cc/nMnK4Ptj)
After speaking with M in SC I decided to go with the self adhesive foam for isolating the cover in lieu of the foam I had laying around the shop that I stuffed in there. I grabbed some today and am well pleased with the results
Title: Re: Radiator Upgrade RZ421
Post by: SoCal250 on January 12, 2026, 12:53:26 PM
Nice and beefy! Looks good on there  :thumbs:
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 12, 2026, 01:29:47 PM
I like it. Hopefully get to test ride today or tomorrow.
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 13, 2026, 10:52:52 AM
(https://i.postimg.cc/13XmNNKK/20260112_155022.jpg) (https://postimg.cc/mPxfvkJc)

Auxito LED headlight bulb installed.
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 13, 2026, 10:53:48 AM
(https://i.postimg.cc/CLmM14bs/20260112_163721.jpg) (https://postimg.cc/Tp5vNg7K)

All back together. Test ride hopefully today.
Title: Re: Radiator Upgrade RZ421
Post by: Simmons1 on January 13, 2026, 11:39:39 AM
 :clap:
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 15, 2026, 12:41:56 AM
I am pleased to report that the 42 MM radiator operational check is a complete success. It was in the 50s here today and I ran it pretty hard. Max temperature observed was 140 degrees. No leaks noted.
Title: Re: Radiator Upgrade RZ421
Post by: 1976RD400C on January 15, 2026, 04:03:15 PM
Next up, the stuck in traffic temperature rise??
Title: Re: Radiator Upgrade RZ421
Post by: Kawtriplefreak on January 15, 2026, 05:57:58 PM
I was in traffic, some but it was 50 degrees outside, and I have a cooling fan. I didn't have a heating problem with the smaller oversize radiator, just trying to make sure I don't.