overheating problems (again)

[MrMelon]

I've fully been having the worst luck with this bike over the last month or so... here's a bit of history:

The bike was overheating and using a fair bit of coolant, so it went into the shop where one of the head gaskets was blown, and a power valve wasn't opening, so $370 later I had new head gaskets and my power valves fixed up. I also had the coolant flushed and replaced.

On the ride home it was going really well.... for about 10 minutes then it started misfiring really badly over 6500rpm. I went into the shop and he sold me some new plugs that were 1 heat range hotter than the last ones.. so I changed them over. The old and new ones are just cheap $7 ngk ones though. The ones that were in there that fouled up were BR9ES's and the ones in there now are BR8ES.

Are these cheap plugs shit and could they cause problems? like would a more expensive heat range 9 plug be less likely to foul up than a cheap heat range 9 plug?

Would changing to a hotter plug increase the likelihood of detonation when the engine gets hot? and could it make the engine run much hotter than it should?

Also I went out for a 20km blast tonight, and after 5km of fairly spirited riding aroudn the bays, the temerature started to climb up from it's regular 60-70 deg to 90-100.. a small squirt in 2nd and 3rd would bring the temp from 90 to 100 pretty quickly. when it got hot the engine wasn't feeling as crisp as usual, and up the top of the rev range there was a little bit of hesitation.

All these hassles are starting to get to me, I just want the fucking bike to work properly!

[Jackrat]

Sounds to me like it,s just running rich mate.
Have that checked out at a different shop.
I don,t know much about the more moden two strokes,but when I was into them many years ago,I would always start with mixture
first,You might also have your coils an leads checked,
Never give a shop a second chance,at that bloody rate they should get it right.

[gpercivl]

You may need to blow out or clean/replace the air filter...this would give the same richening effect if partially blocked.

B8ES plus are fine, we've been running them in MX in YZ-80 and YZ-125 and as long as you're not doing continuous high speed riding, the slightly hotter plugs will give less 'oiling up'. But, if you do find it is the air filters, I'd go back to the B9's.

[marty]

i had a similar problem in the RS - i discovered that non-resistor plugs had been fitted. put new ones in(admittedly @ $20 each) but what a difference! coolant sits at about 51-54 unless i'm climbing the kaimais hard or stuck behind traffic, which doesn't happen very often.....

the standard for the RS is an NGK BR9

hotter is BR10, cooler BR8. i'm running the BR9.

have u been to your manual and checked what the factory fit is?

[bungbung]

Spirited riding eh MrMelon?, I heard you a while before you passed me (and everyone else) in Evans bay...

nice leathers, match the bike.

[MrMelon]

I'll try and get at the air filters tonight to have a look at them and clean them out. The last plugs I took out were carbon fouled, so I think it might be running a bit rich.

With resistor plugs, you can only use them if you don't have resistor caps right? Is there an easy way to find out if you've got resistor caps or not?

I've tried looking through the manual, but it's all in japanese, so doesn't really help me much

Yeah it was just a quick little blast around the bays last night to see how the bike was going and if the leathers fit properly while I was on the bike They seem pretty sweet, especially for $550. Once I get this sorted we'll have to go for a ride some time

I'm kinda thinking that there might be a small air leak in one of the hoses in the cooling system which is letting air in so the water pump can't circulate the coolant properly, but the guy at the last shop I took it to said that he did a pressure test on the cooling system and it was fine. But I don't really know what else could cause it.

[MrMelon]

If what I can find is correct the ngk BR8ES plugs are already resistor plugs anyway :/

The guy at the shop told me the standard plugs were the BR9ES's

[bungbung]

TZR, does it have an alloy radiator? if you can pull off a pipe to look into the core, you can check to see whether or not the alloy has furred up due to no corrosion inhibitor being used at some point in its past life. Furry internals will inhibit heat transfer from the coolant to the airflow.

[MrMelon]

I don't think it's got an alloy radiator, and when i last looked inside there it seemed fairly clean. It seems more like the coolant isn't being circulated at all.

[madandy]

If you get your mixture set right and it still runs hot maybe your water pump is farked?

[Motu]

I don't know much about watercooled bikes,they were newfangled stuff when I was working on bikes.But I work on watercooled cars everybloodyday.For overheating we go thermostat,fans,blocked radiator,waterpump impellor,ignition timing,lean mixture.

We had a 98 Mondeo last week with a cracked impellor,this is not common,maybe 2 or 3 times a year for me,so is the last thing we think of.Best way to test is to crack a hose,then give her a rev - if you get a squirt of water (dump the coolant and test with water,you can spill and waste it) then you got circulation,no squirt and the pump isn't pumping.

[Dave]

First-NGK plug numbers work in reverse-7 is hotter than 8
8 is hotter than 9.
the spark plug heat range does not make the engine run 'hotter'
or 'colder'. Rather it performs at its best in a chamber in a certain heat range.
That is why our race bikes (125GP) are running a 10.5 heat range-we are at full throttle for 90% of the time therefore the engine is under a lot of load and a cooler plug performs better.
if your bike is fouling with an 8 and you put in a 9,it will be worse.
Some bikes need resistors to help the coil to function correctly,they will either have the in the lead,or they have plugs with them fitted.See what the manufacturer says and use the recommended stuff.
If you had a leak in the cooling system,the water would come out-not air coming in.The waterpump may well be damaged-these are usually plastic and quite prone to fail.

[MrMelon]

ok, so I just got a call from the workshop, and he reckons that it's losing coolant, but there are no leaks externally anywhere, and the head gasket definately isn't blown, so he reckons that it's got a cracked barrel that the coolant's leaking through there..

So I took it into him 3 weeks ago telling him it was overheating and suspected it was blown head gasket because it was losing coolant, so he charged me $400, replaced the head gaskets and didn't fix the fucking overheating problem at all.

Reckon's it's going to cost $3-500 to pull the barrels off and check them out... this is bullshit.

 

[Dave]

your right, it seems as though they have miss diagnosed your problems.If you were in auckland i would say come in and see me and lets get the thing figured out.It could be that the head gaskets weren't done properly,or that the coolant is leaking into the crankcase between the cases,or into the gearbox through the internal waterpump seal. Either way i wouldn't trust the people that you used before.-you've mentioned missing-That would indicate that the water is ending up in the camber-so suspect crank case sealing or headgasket.
Cracked cylinders? really whats more likely to leak-a rubber seal, some silicone sealant? or an aluminium cylinder with crome plating right up the inside?-i'd look at the seals etc. first.

[MrMelon]

Well he's got it in there and reckons he was taking the barrels off it today to inspect them and see if he could find a crack.. He's going to pull it all apart and probably have to replace the head gaskets again anyway, so i'm going to try and argue that he should have tested it last week to make sure the head gaskets were actually the problem instad of just replacing them and charging me $400 for the pleasure. So at least the labour component for the last bill should be taken off this one.