LC 350

[lcrob]

Hello all looking to out a bigger radiator on my LC350 any recommendations. Thanks.

[donkeychomp]

Can I ask why you need a larger rad? Is it not cooling properly?

Alex

[rigga]

The alloy rads off eBay have slightly larger capacity, for a direct fit ....other then that, its a Rad designed for another bike, and some Fab work.

[oldelsieboy]

Sept 21, 2021 20:27:32 GMT 1 lcrob said:

Hello all looking to out a bigger radiator on my LC350 any recommendations. Thanks.

www.mb-designs.co.uk/shop/RD-LC-Oversize-Radiator-p253341857

[dusty350]

If your budget can go to a GMX, via Martin at MadBiker, that's what I would get - fantastic quality compared to the Chinese rads;

20190425_191807 by dusty miller, on Flickr

[Tobyjugs]

I dont think the radiator type above is that good.

It struggled to cool my 70 pk bike in warm weather. I now fit wind deflectors in HOT weather and i modified the small de-aeration line to a 2mm diameter hole.

I have one from Norbo which doesn't look so nice as this radiator but it works very well.

[badger1]

Sept 22, 2021 7:12:53 GMT 1 Tobyjugs said:

I dont think the radiator type above is that good.

It struggled to cool my 70 pk bike in warm weather. I now fit wind deflectors in HOT weather and i modified the small de-aeration line to a 2mm diameter hole.

I have one from Norbo which doesn't look so nice as this radiator but it works very well.



Same the mbd/gmx didn’t work as good as I thought it would. Looks pretty to the eye mind.

[Tobyjugs]

Sept 22, 2021 9:32:45 GMT 1 badger1 said:

Sept 22, 2021 7:12:53 GMT 1 Tobyjugs said:

I don't think the radiator type above is that good.

It struggled to cool my 70 pk bike in warm weather. I now fit wind deflectors in HOT weather and i modified the small de-aeration line to a 2mm diameter hole.

I have one from Norbo which doesn't look so nice as this radiator but it works very well.



Same the mbd/gmx didn’t work as good as I thought it would. Looks pretty to the eye mind.

Perfect for a show Bike. Is your radiator connected to a 4L0 engine or a YPS engine?

[badger1]

Sept 22, 2021 10:17:05 GMT 1 Tobyjugs said:

Sept 22, 2021 9:32:45 GMT 1 badger1 said:

Perfect for a show Bike. Is your radiator connected to a 4L0 engine or a YPS engine?

4L0 , std Yamaha impeller. I found overall temperature ridden fast or slow wasn’t much different than the std rad. They did do a even bigger radiator aimed at big bore engines that might be better.

[lcrob]

Thanks all for your pearls of wisdom.

[reedpete]

I think there would be more targeted suggestions if we knew wether you wanted a better looking rad or whether your cooling is a prob. The std. rad is pretty good, on a 4L0 there’s shouldn’t be a thermostat, and the impellers do wear…plus of course general gundge up…
So if you can expand a bit on the motivation for the question, then probably you’ll get convergence on the answers.

[dusty350]

The Gmx rad is working perfectly , with no cooling issues at all. It's in the orange hybrid with the Pv engine, hence the extra pipe below the filler neck.

Dusty

[4l04ever]

Have a look in my rebuild thread...



rdlccrazy.proboards.com/thread/50204/rebuild-number-7-5-lc?page=3

This modified Triumph TT600 radiator is actually a little too large, as in cooler weather, only gets to 50c, so will need to blank a section off. Was mint in the hot weather as never went above 60c.

I previously used a modified Thundercat Radiator, which went up to around 75c in the hot weather and around 58c in the cooler weather.

[jessy03]

The standard radiator works fine with 350lc engine, temperatures start to rise when you add a bigger/wider front end which restricts the air flow in to the radiator. If that’s the case I would add a radiator with a larger surface area, larger capacity won’t all ways work.
Jess

[perazzi350]

I made some defectors for mine dropped temperature about 8 degrees now runs at about 70 also fitted r 6 fan on manual switch if stuck in traffic for longer time

[muttsnuts]

I do 2 sizes of rads for the LC, one which is standard dimensions for mounting brackets etc, but more capacity which is aimed at tuned motors upto around 70bhp, then I have a much larger radiator, one of which is currently keeping a 115bhp LC running at 48c on a hot day, these bigger rads are for big BHP enegines, but a lot of guys have bought them and fitted to lesser powered bikes which keeps them very cool indeed, no complaints thus far........

[JonW]

I fitted a Chinese unit off a Honda quad on my 421 LC with RGV forks. Also has an R6 fan with an aftermarket thermo controller unit. Im considering the need for deflectors on hot days as well if needed.

Info can be found 5/6th way down this page:

www.2smoked.com/Yamaha_RD350_LC_421cc_Athena_engine.html

[JonW]

Sept 21, 2021 22:18:18 GMT 1 dusty350 said:

20190425_191807 by dusty miller, on Flickr

Dusty, Can I ask why you chose to put that head-to-rad connection on the filler side? I did mine on the other side so that the hot water exiting the head went as far away as possible from the inlet at the bottom of the rad. I did that as I was worried the high flow impeller might (probably wont as we know now these dont flow that well) could create enough pull that it drew in hot water were that connection too close. I know the heat will generally stay up top due to convection, but in my mind I was trying to seperate the hot and cold as much as possible so interested to see you/Martin@MBD did it this way.

I should also say that rads with side tanks dont get a good rap from cooling experts, which is weird as so many vehicles use them.

Anyway, depends what youre cooling as Dave says. Not everyone is cooling a big bore engine behind thick forks in a hot city in Australian summer...

[JonW]

Im not an expert in any shape or form on cooling, but in my defence I did a lot of reading about cooling and there are some things the OP (and other people who come along later) might want to think about if doing this.

Rads are not just about size. Ie OEM LC is 750ml, ypvs is around 2/3rds of that. Just based on size you wonder how the ypvs making more power can cool itself stood in traffic. So there is obviously more going on in the engine as the impeller is the same, water pump cover is much the same etc. Cylinders/head are obviously different enough, or was it that 750 was too big or did just adding the thermostat in there make things better... but the LC almost has provision for one, yet they didnt fit it - why was that? The more you learn and think, the more questions you will have I suspect.

Also consider that Forks, fairings and air passing over at speed or standstill all make a huge difference to this too and there are lots of other factors at work here. Drag race engines vs road engines etc etc

Remember just fitting a big rad and/or a high flow impeller may not be the fix to a heat problem, they can just pass the hot water through the system too fast and it doesnt cool fully... or it could cool too much... too cool and too hot both lead to seizure...

And all that said I wonder why a standard LC needs a big rad at all? Maybe you have an issue in the OEM system? it could well be that youve a blockage or the timing is out making it run hot. I believe any need for more than 750ml on a standard LC engine / setup would need a really good looking into, not just throw a big rad on it etc.

FWIW it is always worth checking the casting inside the exit from the pump in the side case. All the brand new 'banshee' side covers ive fitted had casting flashing in that area that needed removal, if you fitted that without work you'd have an issue as some were half blocking the pump's exit flow. I suspect in the factory this used to be picked up and removed by the operator, but that steam member left in the 90s and the newer batches were just cast and painted and put in boxes by someone who wasnt thinking about what this part does. Its always worth checking the inlet and outlet of even old parts to be sure you are getting the flow as designed.

[dusty350]

As standard for this type of rad, GMX fitted the bypass pipe inlet in the middle of the rad - a pig to get to for pipe connections, so I asked Martin to get it fitted on the right side so it was easily accessible. I've seen a few rads on hybrids with the spigot fixed in that position so decided it was as good a place as any. The owner of the bike is a friend of mine and reports everything works as it should, and there are no cooling issues, and that's with an Rgv front end and a Rentec rad guard fitted. I felt that this solution was preferable to blanking off the head bypass and drilling a 3mm hole in the shoulder of the stat which is the easiest option on this set up - and I did that on the first Lc/Pv hybrid I built, and that worked well too !!

Dusty

[4l04ever]

From what I have read up, the LC cylinders do not transfer heat to the coolant that efficiently as the water jacket is too thick. The heat only travels so far into the water jacket, i.e. only the outer few millimetres of the water jacket collects the heat before the water is out of the cylinder. Newer cylinders, like 3XV ones, have thinner water jackets to get maximum heat transfer to the coolant.

By running an oversize radiator on an LC engine, you are making up for the engine to coolant transfer being poor.

[reedpete]

Sept 23, 2021 20:36:35 GMT 1 4l04ever said:

From what I have read up, the LC cylinders do not transfer heat to the coolant that efficiently as the water jacket is too thick. The heat only travels so far into the water jacket, i.e. only the outer few millimetres of the water jacket collects the heat before the water is out of the cylinder. Newer cylinders, like 3XV ones, have thinner water jackets to get maximum heat transfer to the coolant.

By running an oversize radiator on an LC engine, you are making up for the engine to coolant transfer being poor.

Got cast iron liners too….not plated alloy…plus the boundary layer between the liner and the barrel core. Plus thermal transfer in aluminium is much higher than cast iron. 
Then there’s the mono block head, which was fine on the TZ with Siamese Bore, but really the LC should have had independent heads…just the usual production cost and complexity stopped it. 
no matter…as we know they can still be made to properly go ….

[bare]

Erm.. Japanese Market LC 350 were supplied with Thermostats. For reason.
Seems Yama San didn't think Gaijin could deal with the complexity of a thermostat, so it wasn't fitted to export models .
Fit one. The outlet allows for it.

[JonW]

It doesnt tho bare. you need to add a spacer or the themo cant open fully and instead cuts off the water supply.

[4l04ever]

A stat is only useful for two purposes :-

1. good to help warm up the engine quicker in colder climates
2. if the radiator can cool more than the engine needs, then the stat regulates the water temperature, but on an LC this is not the case, as optimum water temperature is not 80c but more like 55c, and the standard rad cannot achieve this, so stat would just stay open all the time.

Other things that can affect cooling are flow rate, and water pump clearance to water pump cover.

[lcrob]

Thanks everyone for your very useful comments.

[JonW]

Sept 24, 2021 16:57:18 GMT 1 bare said:

Erm.. Japanese Market LC 350 were supplied with Thermostats. For reason.
Seems Yama San didn't think Gaijin could deal with the complexity of a thermostat, so it wasn't fitted to export models .
Fit one. The outlet allows for it.

Interestingly, I made the effort to look this up as we know the YPVS stat is too tall for the LC's housing unless you have a spacer as I mentioned before.

It seemed weird to me that the housing for the LC looked like it was designed for a stat, but none was fitted as nothing appears on the parts diagrams for our bikes.

It also didnt need to be so elaborate a casting just for a simple water outlet, so its been at the back of my mind for a long time that something different was planned for this part at the outset and not used on our models.

I had incorrectly assumed that all people fitting stats did so with the later RD/RZ unit and bare's mention of the JDM version having one from new got me wanting to look this up as I realised that the stat used was likely different to the later one and therefore fitted without a spacer.

Perhaps those wanting a stat in an LC would be better served with buying a new stat that correctly fits rather than a spacer? might even be cheaper than a ypvs stat and a spacer?

And it is.

Ok, Looking at the JDM parts books for the RZ350 (the LC is an RZ of course in Yam parlance, the whole RD thing was local marketing departments holding on to model ranges abroad).

From what i can tell from the parts books i found. In 1980/1 Yam did not fit a stat to the RZ350, but did in 82 as thats when it appears on the parts diagrams. I didnt check the RZ250 which was the main model in Japan of course.

It is part number 717-12411-00-00 and is the same stat used in the TZ. Which makes sense for many reasons.

Why dont many LCs have these? Probably cos of what Rob says here, the LC warms up quickly and doesnt get the coolant low enough to need one when running, even in Canada / EU where temps are low. Weird that Japan had them tho... but maybe dealers removed them on first service like they did with the exhaust restrictions on the UK 350Rs etc. Just cos its fitted doesnt mean its needed sometimes.

[reedpete]

Quick warm up helps emission during start up. Probably an issue in JDM at that time.
But your findings make me curious about usage on the TZ, seems slightly counter intuitive to put one on a race bike. However maybe it was designed in in case it was of use but generally not used….need to ask those that know…

[JonW]

I have a mate with a TZ, I can ask him. There are a lot of years and models of them tho, plus even if his hasnt got one, we probably will never know if it started life with one. hmm...

[JonW]

Link to one of the TZ parts books, not showing as 'optional'

www.partzilla.com/catalog/yamaha/motorcycle/1974/tz350/cylinder-head-cylinder-tz250-tz350