Is 3/4 on the temp gauge normal?

[Nismosis]

Hello to you all,

I am new to this forum and this is my first post.

I recently bought a restored MK1 RD125LC and I’m very happy with the bike. I went for a ride at the weekend for the first time and what a lovely bike it is to ride. Nothing below 6000rpm and then off we go 

Once the bike had warmed up and I started to open her up a bit I noticed that the temperature gauge moved to approximately ¾ along the gauge. It pretty much stayed there for most of the journey until I got towards the end (say 30 miles) where I rode up a long steep hill (about a mile long) and I was in 5th at 9000rpm all the way up. When I got to the top I notice that the needle had moved above ¾ and was approaching the red, it didn’t go into the red but was above ¾. It was a warm day around 24 deg but nothing mental. The bike has a Micron fork brace fitted and I’m wondering if this maybe deflecting air away from the radiator or disrupting the airflow. It runs a standard de restricted exhaust, 10W carb and Castrol Racing 2T 2 stroke oil.

Is this normal for the RD125LC?

A few I’ve talked to said this is pretty normal especially on a warm day but I just wanted to check as if there is a problem I don’t want to seize the engine.

All the best

Gary

[Nismosis]

Oh yeah, that's my Dad on the bike by the way.. I think the bike mike struggle a bit with him riding it (bless..) :-)

[crash]

my mark 2 rd 125 lc back in the day did not go that high ,but it was brand new at the time.

[jaylee22]

that is too high, you can probably smell the bike getting too hot as well. i'm having the same problem with one of mine!!! here is a list of what i've checked so far;

1.water pump turning properly.
2.no bubbles or oil in coolent. (poss leak)
3.air lock in cooling system.
4.correct temp sender.
5.engine running lean.(not enough fuel oil mix)
6.oil pump working properly.

etc etc good luck and if you find something i've not mentioned besides the obvious, give us a shout;-)

[sheadhead]

new to forum but ive had 3 lc 2mk 1 and a mk2 and they all ran about that temp

[broughton5]

my mk1 gets to half way at the most also check rad cooling fins are in good order and are not blocked with dirt or debri also check rad level

[looey]

That's too hot for sure.

About 1/3 up the green is normal on a warm day. I took my Mk1 out Sunday, it was 27 degrees outside and even after a good 30 min brisk ride (mostly in the power band it didn't even get as high as half way.

I won't be the Fork Brace as I have an identical one fitted.

Check all the things that have been said. Either there is a cooling problem or possible the sender or guage are not right

Good luck

[Nismosis]

Cheers for the reply lads. I checked the coolant level and all is well, fired her up with the rad cap off and squeezed the hoses to se if any air was trapped. the radiator is filled to the brim and the expansion tan is on the F mark.

I seem to remember the guy I bought it from (Jackup on this forum) said that as it has a 10W carb and derestricted standard exhaust he put a 150 main jet in the carb. I'm sure it's fine but maybe it's running lean (fuel & oil) causing it to get hot? Would I benefit from a bigger main jet or does a 150 sound right with my set up?

the fins on the rad are pretty good, a fwe ben ones but only a small percentage. Standard cover too. maybe it is the temperature sender/sensor but I just can't seem to find any for sale??

Cheers

Gary

[mrnegative]

check your plug to see how its running?

[looey]

155 is the standard main jet size for a 10w carb but maybe it's ended up with a 150 after some fettling ?.

Wouldn't have thought that would make enough difference to show hot on the temperature gauge ?. We are talking about the water temperature in the head here, not the piston crown temp.

Like Mr Negative has said it's worth checking the plug colour to see how it's running mixture wise.

Might be worth sending Mr jackup a PM on here, nobody's gonna know the bike better than him ?.

[raccoon]

my mk1 runs about 3/4 the way up the gauge thats with the bigbore on as well, i was talking to a couple of guys with standand mk1s and theres are the same so it must be pretty normal, i would say optimal running temp is around 80deg if it hits the red it must be around 100 deg and thats to hot.

[snowbound]

My Mk1 runs about 1/4 to 1/3 on the temp gauge.
1.5mm over bore
Running K&N cone filter.
12a carb with a 220 main jet
Nikon exhaust.
pre mix fuel:oil @ 40:1

[jackup]

155 main jet fitted if your that worried I will send you a bigger jet? But it will screw up your cold starting

[Nismosis]

Ahh sorry Jackup, it's a 155 (for some reason I had 150 in my head). To be honest the bike runs great and I'm very happy with it. I'm just a bit concerned about the temperature. It seems like everyones bikes run at different teperatures, or maybe they all run similar teps but its the gauge/senders that are giving different readings?

If I knew I could just ride it with 3/4 showing on the gauge and it would cause no harm to the bike then I'm fine with that, I'm just concerned that prolonged riding with engine running hotter that normal my cause damage over time.

If I were to fit a bigger jet would I have to adjust the air/fuel mixture screw? Also would I need to adjust the oil pump or is it just a case of fitting the bigger jet and away you go?

I'm still learning about these bikes (and 2 stokes in general) so sorry for all the questions.

Thank you all for your information and help :-)

[jackup]

Riding it at 3/4 temp wont do it any harm
If you want to up the jet I would only go 2 sizes bigger (165)
Don't have to change oil pump at all
might have to adjust air mix screw
Before you decide read the carb section on the forum all the info is there for you to learn what you need to no.
The carb on the bike is very tricky to get back in due to the reed spacer if you want to do it give me a bell and I will talk you though the best way remove and the hard part refit it

[neil]

mine runs between half and 3 quarters. i noticed the needle moves up with vibrations too. a good rad is a must, had lot of problems with my mates running hot till we found a decent rad.

[looey]

Well I agree that it shouldn't do any harm running at 3/4 temp but I disagree that it's normal.

It's probably normal on most 30yr old RD125LC 's that are not running with optimum cooling due to slightly furred up rads and water jackets in the barrels and head etc. but if they are std bore, and cooling as they would've from new then about 1/4 - 1/2 is normal.

As has been said it could be the gauges or senders.

I've had one brand spanking new and it ran about 1/4 - 1/2 on the temp gauge whatever the weather and however you rode it (as does mine now).

I run a 170 main jet but my bike is a completely std 10W just with a later style Micron exhaust

[Nismosis]

Hi Jackup,

Ok mate, I might give the 165 main jet a go and see if it runs a bit cooler. Can the jet not be replaced with the carb still in place? Can I not just loosen the carb clips (airbox and intake) then remove the throttle slide and any fuel/oil pipes, then rotate the carb 90 degrees so I can remove the float bowl?

If I did have to remove the carb can I not just undo the 4 intake bolts, slide out the spacer and then remove the carb that way?

One final question…. To richen the air/fuel mixture do you turn the screw anti-clockwise?

If you have a 165 main jet I’d be happy to buy it off you.

Cheers

Gary

[Nismosis]

Hey Looey, where abouts in Surrey do you live? I’m just off Junction 9 M25, maybe we could meet one weekend say at Boxhill? Just a thought….

[Norbo]

doesd irt have a chrome rad guard on with small round holls or a srandard plastic one fitted

[Nismosis]

it has a standard Yamaha cover. I might whip the rad off and just straighten any bent fins then give it a hoover to remove any debris/flies etc..

[Norbo]

Then it should be fine the old renteck one blocked air intake but the standard ones are fine . so long as it does not go in the red or get to close you will be ok . ive had mine 3/4 the way lots of time and nothing hapend . but id do a plug chop any way to be on the safe side.

[Nismosis]

Cheers Norbo, nice to talk to you on the phone the other day too (I was the one that ordered the Mirrors, filter etc.) ;-)

[jackup]

You can tilt the carb as you say but it's super tight I didn't have a 165 jet so I've ordered one from yambits and should be with you soon as I've used your del address.

[Nismosis]

That's very noble of you Jackup, let me know the cost and I'll trasfer the money.

I don't want this thread turning into 'Im not happy with the bike' I am very happy with the bike. It maybe something simple, it probably is and I'll keep you posted on the result.

I need to do a plug chop and I'll go from there. If it looks fine then I know it's not running lean. I may try a plug chop with theh 155 and the 165 and see what diffence there is.

[jackup]

Don't worry about the cost it's peanuts glad to follow up any bike I sell

[looey]

Aug 16, 2012 9:59:12 GMT 1 Nismosis said:

Hey Looey, where abouts in Surrey do you live? I’m just off Junction 9 M25, maybe we could meet one weekend say at Boxhill? Just a thought….

Yeah there's a group of us always out on 2-strokes at weekends. I'll send u a PM mate, keep an eye out for it

[Norbo]

Aug 16, 2012 18:03:13 GMT 1 jackup said:

Don't worry about the cost it's peanuts glad to follow up any bike I sell

What i nice bloke . How many people would do this for you.

[Nismosis]

That's very nice of you Jackup, thanks very much. I'm out tomorrow morning up to Boxhill, looking forward to it :-)

[looey]

If you're going down to Boxhill then get yourself down to the Classic bike show in Capel. It's only a few miles from Dorking/Boxhill.

The show is on from 12pm - 5pm.

Me and the misses will be there on our GT250 X7's with a few friends

We'll probably pop into Boxhill on the way, around 11:30am I woulda thought.