1986-88 1TX overheating

[Alf]

Hi guys

My 1TX is finished and working fantastically after a top end refreshing process. Even in the running in period I can feel the difference in compression: the cylinders were ovaled

But... the overheating continues. Its true that only in very aggressive sport-riding and uphill on very tight roads, today with 25ºC hot, (that it is even hotter riding on tarmac). But my 3CV don't overheat

Settings: KN replacement filter in OE box, Dynojet kit, std Stage 1 except one shim under the needle, 5º advancer, open cans with STD headers and pan, colder plugs. I've polished head intakes. RPM cooler

My 3CV carry on similar settings, without the shim under the needle, but 4º advancer and open non-std pan and a narrow cooler than Randy's, even wider than OE. The cans are a bit less opened, but not too much (1 cm)

The carburation in both is spot-on, at sea level or 2000 m altitude (not too difficult to check here, 30 km. between both) and now it is possible that my 1TX run faster than my 3CV. Only possible, I've not perform a side to side test. Polishing the intakes has given a turbo-like thrust at 7000 rpm on

We are running off new ideas about the overheating problem.  The last 3 are:

1.- Dismount the 5º advancer and fit the OE one
2.- Set the fuel level at maximun
3.- Check the oil pressure...but if the oil pump is 2 in 1, and the part on charge of the cooling is bad, the pressure indication don't say anything, right?

Maybe the fuel level on cubes are not maintained for the vacuum system in extreme situations, hence Yamaha fitted the fuel pump?

And no, it is illegal to fit Unipods in Spain

And yes, I can remove the oil thermometer. But It is not a solution   

Any idea would be welcome. Thanks

[Starquest]

Hola, Alf. Jose, from Florida. The overheating occurs at see level or at 2000m ? What size of main jet are you running? According to dynojet #120 main is equivalent to 112.5 mikuni. May be you are a little lean at the top.

[Pat Conlon]

How hot?

[Tuned forks]

How hot?

That's kinda what I was thinking. How is the OP quantifying "hot"?

Joe

[fj1289]

How hot?

That's kinda what I was thinking. How is the OP quantifying "hot"?

Joe

From a previous related thread - he is going off oil temp senders and gauges installed on each bike.

[Alf]

Hola, Alf. Jose, from Florida. The overheating occurs at see level or at 2000m ? What size of main jet are you running? According to dynojet #120 main is equivalent to 112.5 mikuni. May be you are a little lean at the top.

Thanks

The overheat occurs on sport hard riding going uphill
Dynojet mains have a different design from Mikunis and are not equivalent. Apart that I´ve tested a bigger mains, that dont work, my 3CV would be even learner by that rule, and it is not because the problem is not present

[Alf]

How hot?

Hi Pat. Happy to chat with you 

120ºC oil temp in 8 km on an slow, tight road. It is the most extreme condition. Granadilla-Vilaflor TF 21, if you like to have a look on Maps
My 90 model arrives at the end of the road, 15 km, at 115-118ºC, and continuing uphill for the faster road from Vilaflor the temp goes down

Moves:

1.- setting the fuel level at maximun on cubes. Its a pity because the bike runs perfect in any circumstance and altitude
2.- dismount the 5º advancer
3.- fit a fuel pump to maintain the fuel level on cubes
4.- change the oil pump (Maybe the oil cooler part of the pump is not working correctly?)

But in my friend Mingo´s 86 this uphill overheating problem is not present. Yes, the fuel settings are different, but if the problem is the vacuum system no providing enough fuel on uphill roads, the problem will be present too, and it is not the case

I'm running of ideas

[Alf]

From a previous related thread - he is going off oil temp senders and gauges installed on each bike.

Yes, right. And both bikes are carefully carb set and tested. And I bought a laser gauge to check temp at the base of the oil filter and to check the accuracy of the digital oil temp gauges

[Bones]

Alf, I remember reading an article a few years ago concerning the FJ and overheating. Apparently it's a common problem and the cause is the cam timing. The fix is to either advance or retard the cams a couple of degrees which cures it and gives better throttle response. Ive been looking everywhere trying to find the article but can't seem to find it.  Tony.

[fj1289]

Alf, I remember reading an article a few years ago concerning the FJ and overheating. Apparently it's a common problem and the cause is the cam timing. The fix is to either advance or retard the cams a couple of degrees which cures it and gives better throttle response. Ive been looking everywhere trying to find the article but can't seem to find it.  Tony.

https://www.hotrod.com/articles/ctrp-9908-building-a-better-engine/


I also recall another article - but my google skills are failing me right now.   As I recall they set the crank the "universal" 105 centers as made popular by Pops Yoshimura 

[fj1289]

The cars stress these engines so much more than any street driven FJ ever could (assuming it is taken care of and receives basic maintenance) 

[Alf]

Alf, I remember reading an article a few years ago concerning the FJ and overheating. Apparently it's a common problem and the cause is the cam timing. The fix is to either advance or retard the cams a couple of degrees which cures it and gives better throttle response. Ive been looking everywhere trying to find the article but can't seem to find it.  Tony.

https://www.hotrod.com/articles/ctrp-9908-building-a-better-engine/

My 90 is okay with 4º advancer. Maybe only 1º more, 5º advancer, could be the cause of the overheating?
Firts thing: next saturday I´m going to remove it and check. I will inform
Thanks 

[Pat Conlon]

Cam timing modification: I did ask this question 11 years ago, here's the post:

http://www.fjowners.com/index.php?topic=712.0

Speaking of cam timing....Alf, have you verified that your current cam timing is correct?
Sometimes the cam chain can stretch and get the cam timing off....

[FJ_Hooligan]

Pat,

Rereading that cam timing thread brought back old memories, both good and bad.

I think I still have a copy of the FJ cam timing article that Joe Minton wrote for Cycle Magazine back in the '80s.

[aviationfred]

I did a conversion for your oil temp. 120°C = 248°F. During the summer and riding in my area, the temps easily get to be 95-105°F and the oil temp will often reach 124°C/255°F while sitting in traffic. I have been told by Randy and Robert that these high temps are ok. The Legends racecars often run 127°C/260°F while at WOT on the track. I personally would say things are ok on the 1TX.

Fred