1987 Honda 350d spark-no spark

[AKATV 822]

3 hours ago, Goober said:

I would try baking one of the FCU in an oven to see if you can revive it. 
i would try 200F for at least 3 hours. Let cool completely before you reinstall. See if that improves.

as last resort, bake in 450F oven for 5 minutes. This may cause smoking or burning electrical smell 

I dont want to bang heads Goober, but I just wanted to ask what  the expected repair result of warming at 200F degrees is?

These units are watertight due to being embedded in epoxy so they are not "drying out" unless the plug is wet and you can blow that out with compressed air

The vast majority of these FCU'S and CDI's go bad due to fractured solder joints on the internal, potted (epoxy covered) circuit board and the only way you are going to reflow the solder is at a temperature where solder melts. 60/40 electronic solder melts at 220-240C or 428F-464 F

 

 

 

 

[AKATV 822]

3 hours ago, Jared k said:

Yes tapping either one on tire decently causes oil light flicks, fan on and off- back and forth... so this concluded two faulty fcus?

By tapping these and having it flicker, you are confirming broken or loose solder joint inside or (least likely) a stuck or sticky relay

Baking these at a correct temperature to melt solder will reflow the solder joints

Years of heat and vibration take their toll on the 30+ year old solder joints and they fracture, especially if it was a "cold" (bad/brittle) solder joint at the factory

 

[Jared k 14]

So are we saying bake at 450 degrees? 

[AKATV 822]

You were baking it 3 hours ago-did it work?

450 degrees @ 10 minutes Is what I have done for years, not saying its a miracle cure but has worked on GREAT percentage of failed modules

If it doesnt work you can try it a second time-if no,t no harm as you needed a new one anyways...

If you want to try at 200 first its up to you. 200 degrees will not melt solder, the best it will do it warm it up enough to possibly bridge the fracture joint due to expansion and it might work until it cools down or vibration separates the joint again

450 will reflow (melt) the solder joint and yes it makes an odor as the plastic case and potting epoxy heats up etc, which is normal.

It should not smoke unless you have grease and dirt all over, so clean it up first

I have a thrift shop toaster oven in the garage and check temperatures with laser temp gun

Let us know how you make out

 

[Jared k 14]

Yes I baked it at 200 for 3.5 hours and pulled it out and it’s still cooling... I planned on trying it later this evening but after reading a couple of these I think I may throw it back in at 450 for 10-15 mins? Just to know for sure it was worth while

[Goober 1,555]

AKATV I know you found that 450F can result in a good fix; I’m sure you know more about these circuits and I appreciate you for it. We’re not going to bang heads because i think you’ll agree that high heat method fits into a diagnostic chain if you will.

i like to start out by recommending a contact cleaning, pin inspection and lube before trying anything else.

then I bake the modules at the lower temperature as a diagnostic tool. Before you mentioned it i had only ever heard about Shadetree heating these modules with a hair dryer. I didn’t know why it worked but i thot maybe moisture or mold or sealant warping. I had never heard of anyone heating them in an oven at any temperature; so I tried it on a TRX300 FCU which is BTW hard to find, and it worked. For about six months.

After hearing how you do it I’m now willing to try that high heat method on my FCU. But only because I’ve tried those first two steps.

 

 

[jeepwm69 7,611]

I baked the 450 module Fishfiles sent for me (dead on arrival) for 8 mins in a preheated toaster oven set on 450.

 

Wife chewed my a$$ about the smell.  Fan module works now.

[Jared k 14]

Ok so I hooked up freshly baked and cooked fcu and it’s too late to fire it up now so I will test in morning but my oil finally cooled down to 78 degrees... I believe with current temp here that’s the best I’m going to get and my oil temp sensor is a solid 8.72 olms.... should I consider it out of range and bad based off of that reading? 

[Jared k 14]

Update... at 76 degree oil temp- the sensor gives reading of 9.47olms- I would assume that’s pretty darn close to what the book wants of ( 77 degrees- 9.5-10) , any thoughts?

[Goober 1,555]

I think that’s good rather have it low than high. The colder it gets the higher R value. It’s possible that it goes to zero too quickly but you won’t be able to measure unless you run it til it gets hot and then measure both.

Edited August 17, 2022 by Goober

[Goober 1,555]

I learned from @retro how to rebuild these oil temp sensors. I was planning on building some of his homebuilt fan controllers but got sidetracked. I met a couple of TRX350 owners who needed a sensor so i traded and sold them. Even a used sensor these days is going for $80 to $100 and I don’t understand why!! Most used sensors the R value is too high for kicking on the fan at 212-220F—instead you find them coming on at 245F! That’s pretty hot.

 

 

 

[Jared k 14]

That’s a valuable hobby if you ask me LOL...it would be nice if there were actually aftermarket parts available for this machine but everything worth buying seems to not be made anymore so you have to risk a used oem part..

How about valve adjustment on it? There is a bit of valve train noise coming from it so I’m hoping/ assuming perhaps just a simple tightening up is what’s needed...

[Goober 1,555]

Yeah couple of the members here can describe how to do cam chains real easy.

you can check cam chain slack by measuring how far in you can push in the cam chain tensioner once you pull it out and extend it. Then retract it and reinstall it.

 

Edited August 17, 2022 by Goober

[Jared k 14]

So finally tried the oven baked fan control unit, started as normal and ran about 9 minutes and now dead- zero spark. I feel like I keep hitting dead ends. 

[Jared k 14]

Ok so the next question is all the places I look and all availablity of the fan control units do not specifically say 350”D” the “d” isn’t in any of the descriptions.... will/ or should it still work( assuming is in good working condition)?

[jeepwm69 7,611]

https://www.partzilla.com/product/honda/38710-HA7-671?ref=8023f93ab176944bf398d8d5a2829c0a21a1cc15

 

Looks like the 86 and 87 350A fan module will work on the 87 350D as well.

 

The CDI, on the other hand, is 87 350D specific

 

https://www.partzilla.com/product/honda/30410-HA7-751?ref=8023f93ab176944bf398d8d5a2829c0a21a1cc15

 

If you look at the bottom right at those links, you'll see "related fitment" which will tell you other machines that a specific part will also fit.

[Jared k 14]

So at what point would I consider the fcu to not be the issue and the cdi to be problematic? 

[AKATV 822]

Have you been baking the fan controller unit for a spark issue?

To my knowledge the fan controller only controls the fan and the temperature light

When you lose spark try tapping on your CDI while cranking and see if your spark comes back

if so, then you can try baking the CDI module to see if it fixes your spark issue

Edited August 17, 2022 by AKATV

[Jared k 14]

Yes it is all a no spark issue after about 10 minutes of running and then zero spark. I hadn’t thought of baking cdi... same procedure? 450 degrees for 10 mins?

Thank you all for your input and suggestions!!

[AKATV 822]

For a spark issue the fan controller has absolutely nothing to do with spark

I would look at your CDI and I would look at your voltage regulator- I think Jeep mentioned earlier to check your voltage regulator as well

see what your voltage is on your battery with your machine off and then check your voltage with the machine running and give it about a quarter throttle it should be higher than your battery voltage and not exceed 14.5vdc

When you lose spark pull your spark plug 

And lay it on the cylinder head like you normally would check for spark

Then while cranking, tap on the CDI with the handle of a screwdriver give it a few sharp raps and see if it sparks at all 

If it does you can bake it

Don’t forget to check your stator output to your voltage regulator as well as your pulse generator and coil

Do you have the Honda Factory service manual for your machine if not download it from the service manual downloads so you can use the correct procedures

I’m not 100% sure but I think you have a DC CDI Which is a different than most CDIs So you need to make sure that your voltage regulator is charging your battery and your battery is good

 

 

 

 

 

[Jared k 14]

Yes I have the manual, I have went through almost every trouble shoot in it. I did check voltage off and running and throttle - it was about 12.6 off , and under throttle it went to about 14.5. I checked pulse generator and it was 330 olms as required . I checked primary and secondary coil test and it passed. Stator voltage I’m not sure I did that..? Something is killing spark after about 10 minutes of run time and then doesn’t return until engine cools down a bit . I will try the cdi tapping later this afternoon thank you

[AKATV 822]

OK sounds like you’ve got it covered

Were you checking the other components while it was hot and you had no spark as well?

it could be possible that your spark plug is failing as well- have you tried a different spark plug?

Edited August 17, 2022 by AKATV

[Jared k 14]

I was checking after it dies, after it sits, kind of an ongoing several week back and forth kind of thing LOL. Yes I put new plug on per manual spec too

[Jared k 14]

Ok so update, I ran it until it died and then pulled plug out and held against the head and tried starting it while rapping on the cdi box a little and got a few random flickers of spark sporadically... should I try baking it experts?

[AKATV 822]

Yes

450° preheat the oven put it in there for 10 minutes let it cool to the touch and give it a shot it doesn’t work all the time but I’ve had 80% or better

let us know how it goes