Topic: Washed the bike, now it won't start !? Update & questions !

[strynboen]

yes good idea ...i used a spray can for flovers..took the tank off..put on a tank from a brigss& stratton..and startde the engine ,,,and sprayed on the ignision parts...mine coils vas bad..an´d small lightings jumped  from coil..to frame..


still have some small problems in rain..think this old hondas just dont like rain

[Viktor.J]

This is how this turned out so far.

Since I prioritize to ride this summer I just stayed out of the water
But the last two days I went for a trip over to Denmark. Beafore this I washed the bike and then used compressed air to dry it up, worked fine, the bike started directly. I then Used a big hose with a lot of preassure, blowing the water in the air and creating a heavy rain. I did this while the bike was running for about 2 minutes and nothing happend, great !

Back to the Denmark trip, At the middle of the Great belt Bridge it started raining, since it was a bridge and 70 mph highway I coudln't stop. I drove in the rain for about 15-20 minutes and about 20 km before the engine totaly dies flat.
I was standing on the roadside, in the rain, with trucks passing by at 70 mph 1,5 m from me. Me and my friend first tried to keep her running on idle to "dry" up the wather, but she didn't go right. she didn't rev past 2500 rpm cause then she died, the same if I tried to release the clutch in gear. So we removed the point cover - No water or moist (what I could See). When then removed the tank and cheked the spark plugs, they now looked quite dry, checked some bullet connectors etc. now about 30 minutes on the roadside have passed and I said " this is the last time we try, then I'll give up". We tried, and VROOOOM.

At this time I noticed that the exaust pipes had become yellow/blue at the bend out from the cyllinders due to heat. What could cause this extreme heat when just reving around 2000 rpm ?
Are my pipes ruined ? or can I somehow polish it away ?


I dont really know what to read in from this, but it seems that somewhere at the sparkplugs, coils etc I get moist. Beacuse that's were we where "fiddling" and after that she started right up.

So Im planning on changing the ignition system - Ignition, coils, spark cables and spark plugs. What is the most reliable systme out there ? Dyna S ? Hondaman ? Stock ?

[dave500]

boyer bransden,get the micro power unit,frees up a lot of battery charging potential aswell.

[Viktor.J]

boyer bransden,get the micro power unit,frees up a lot of battery charging potential aswell.

Any more info ? I also like to ad, im no electrician

[dave500]

have a look here,i bought one from here,ive had a few boyers,some people seem to associate any english electricals with lucas,which these are far from.
http://www.gremlinracetech.com/product/BBMP

[Viktor.J]

have a look here,i bought one from here,ive had a few boyers,some people seem to associate any english electricals with lucas,which these are far from.
http://www.gremlinracetech.com/product/BBMP

It sounds good is it hard to adjust the retardation/advance of the ignition ? I want a system that can handle water desent and is maintainable by me or a motorcycle mechanics ..

[dave500]

once any electronic ignition is installed it wont need to be adjusted again,,unless you take it apart again,,the boyer unit does away with the mechanical advancer weights and springs,the advance is electronic,a true electronic ignition,easy to install,the normal boyer digital system works with your standard coils,,the micro power unit must only be used with the supplied coils wired in series.

[Xnavylfr]

Do you still have the STOCK air box attached to the carbs???  If you have ANY kind of air filters other than stock you WILL have problems with water getting in the carbs. The rain hits the petrol tank and then runs back and down off the tank right on top of the air filters. IF you have POD air filters , make some sort of cover over the top of them to prevent water intrusion.. The exhaust pipes will turn blue if your engine is running LEAN on fuel.

Still get some DIELECTRIC GREASE and open your KILL switch housing and cover the wire ends with the grease. This PREVENTS water from causing contact between wires in a heavy rain or a WASH job!

Xnavylfr(CHUCK)

[Viktor.J]

Do you still have the STOCK air box attached to the carbs???  If you have ANY kind of air filters other than stock you WILL have problems with water getting in the carbs. The rain hits the petrol tank and then runs back and down off the tank right on top of the air filters. IF you have POD air filters , make some sort of cover over the top of them to prevent water intrusion.. The exhaust pipes will turn blue if your engine is running LEAN on fuel.

Still get some DIELECTRIC GREASE and open your KILL switch housing and cover the wire ends with the grease. This PREVENTS water from causing contact between wires in a heavy rain or a WASH job!

Xnavylfr(CHUCK)

Thank you Chuck, but fortunately im not that stupid
I run stock airbox.
I now that a lean mixture would could torn the pipes blue, but why should they do that after a small period of time, running in teh rain ? That means rain has to cause it. My only "possible" ide is that moist messes up the ignition/coils causing it to fire and missfire constantly, creating irregular and non timing ignitions and this somehow made the exhaust warm.

Here's pictures of the pipes, notice how cylinder 3 show no signs of overheating. Is this misscolor removable ?

[Xnavylfr]

It looks to me like #3 cylinder has NOT been running as hot as 1/2/4. In the second picture it looks like 1/2/4 are all dis-colored and #3 isn't.  It doesn't take long for the pipes to color if it is lean because the engine runs HOT.


Xnavylfr(CHUCK)

[Viktor.J]

It looks to me like #3 cylinder has NOT been running as hot as 1/2/4. In the second picture it looks like 1/2/4 are all dis-colored and #3 isn't.  It doesn't take long for the pipes to color if it is lean because the engine runs HOT.


Xnavylfr(CHUCK)

No dissrespect chuck, but that observation is posted in the previous post. The question is, how could rain/water cause this overheating and is there a way to remove it ?

[TwoTired]

Read about your run stoppage in the rain, and how it differed from spraying the bike, and how it would not rev above 2500.

These symptoms fit water in the carb bowls, as the main jet and slide needle metering jets sucks the liquid from the bottom of the bowls.

There was some discussion in prior threads about the overflow drain tubes sucking up water while riding in the rain.  These tubes were rerouted to a different pressure area for a cure.

I will ask if you have carb vent tube attached to the carbs as well as the overflow tubes at the bottom of the bowls.

[Viktor.J]

Read about your run stoppage in the rain, and how it differed from spraying the bike, and how it would not rev above 2500.

These symptoms fit water in the carb bowls, as the main jet and slide needle metering jets sucks the liquid from the bottom of the bowls.

There was some discussion in prior threads about the overflow drain tubes sucking up water while riding in the rain.  These tubes were rerouted to a different pressure area for a cure.

I will ask if you have carb vent tube attached to the carbs as well as the overflow tubes at the bottom of the bowls.

And after a while the water would then vaporise = ordinary gas in to the cylinders ? If I dont remember wrong the breather tubes are routed downwards towards the rear tire = har to get wather from there up to the carbs.
Is there any other way water could enter the carbs ? if there was places big enaugh for water intake during rain, wouldn't that affect the bikes normal performance (it runs great oterwise)

[Viktor.J]

Here's how she runs now, any signs of sucking air ?

 First a cold start after she's been sitting for 3 days after I washed her (didn't) start her after that.
Cold start after Washing and sitting for 3 days.

Then one when she's a little warmer after 2-3 runs up'n'down the road.
A little warmer, cb750


And here's a picture of the carb overflow tubes, directed down and back.


There's 4 tubes on the last pic, might be hard to see.

[Xnavylfr]

Your third picture shows the carb overflow tubes, Just behind them is the scoop for the air box, water can be sucked in there but not enough to kill the engine. I wouldn't think water would be sucked through those to the carb bowls!  Between #1/2 carbs and #3/4 Carbs close to the top you have a VENT hose to help allow AIR in to the carbs AND some water but very little. This sounds more to be an electric problem than water in the carbs. I've ridden a CB750 in some VERY HEAVY rainstorms (Hurricane) and not have a bit of trouble. There are so many electrical connections on a stock CB, that if they get REAL wet they will make contact through the water and ground out( short to earth)and kill the bike. You have the Kill switch, coil connections under the tank. The connectors on the coils are just plain blade connection and if the get wet they WILL send power to the frame and not the coils.  Some problems just takes time to find.
As for the pipes bluing ,here is some info!!
http://www.finishing.com/148/57.shtml

Oh , NO disrespect taken!!

Xnavylfr(CHUCK)

[TwoTired]

These symptoms fit water in the carb bowls, as the main jet and slide needle metering jets sucks the liquid from the bottom of the bowls.
I will ask if you have carb vent tube attached to the carbs as well as the overflow tubes at the bottom of the bowls.

And after a while the water would then vaporise = ordinary gas in to the cylinders ?

No.  Water would sink to the bottom of the bowls, be sucked into the engine and out the exhaust with enough engine cranking.  However, air/water doesn't burn anywhere near as well as air/fuel. 

If I dont remember wrong the breather tubes are routed downwards towards the rear tire = har to get wather from there up to the carbs.

Not if you think of those tubes as a drinking straw.
This is why I asked about the carb's vent tubing (Item #32).  All the small tubes feed the same chamber above the normal fuel level inside the carbs.  If you put a lower pressure on the vent tubes above and a high pressure on those overflow drain outlets at the bottom, fluid can be drawn up the overflows and deposited into the bowls.

Is there any other way water could enter the carbs ? if there was places big enaugh for water intake during rain, wouldn't that affect the bikes normal performance (it runs great oterwise)

IF it is drawing water up into the carbs from the bottom, the symptom would only show in wet operation, and probably begin after the bike was in motion, as that is when different pressures occur about the various components of the bike due to aerodynamic principles.

The pictures you posted only show 4 small tubes at the bottom.  Doesn't this bike have two more vent tube routed from near the top of the bowls (item #32 in the fiche).   These should route to the same place as the #33 tubes near the swingarm, so they all receive the same pressure, and prevent liquid circulation travel through them (apart from gravity effects).
http://www.westernhillshondayamaha.com/fiche_section_detail.asp?section=2560070&category=Motorcycles&make=Honda&year=1975&fveh=132839

[reddyvv]

What are the electrical connections you have down there hidden behind the vent tubes? Looks like those would get wet in a hurry. I hope they aren't the wires going down to the points.

[kpier883]

Did you take your spark plug wires apart and check them?  I used to have a lot of problems in the wet weather until I pulled the plug caps off, cleaned up the connections and packed them with dielectric grease before re-assembly.  I think water was getting into the caps and causing problems. 

[Viktor.J]

These symptoms fit water in the carb bowls, as the main jet and slide needle metering jets sucks the liquid from the bottom of the bowls.
I will ask if you have carb vent tube attached to the carbs as well as the overflow tubes at the bottom of the bowls.

And after a while the water would then vaporise = ordinary gas in to the cylinders ?

No.  Water would sink to the bottom of the bowls, be sucked into the engine and out the exhaust with enough engine cranking.  However, air/water doesn't burn anywhere near as well as air/fuel. 

If I dont remember wrong the breather tubes are routed downwards towards the rear tire = har to get wather from there up to the carbs.

Not if you think of those tubes as a drinking straw.
This is why I asked about the carb's vent tubing (Item #32).  All the small tubes feed the same chamber above the normal fuel level inside the carbs.  If you put a lower pressure on the vent tubes above and a high pressure on those overflow drain outlets at the bottom, fluid can be drawn up the overflows and deposited into the bowls.

Is there any other way water could enter the carbs ? if there was places big enaugh for water intake during rain, wouldn't that affect the bikes normal performance (it runs great oterwise)

IF it is drawing water up into the carbs from the bottom, the symptom would only show in wet operation, and probably begin after the bike was in motion, as that is when different pressures occur about the various components of the bike due to aerodynamic principles.

The pictures you posted only show 4 small tubes at the bottom.  Doesn't this bike have two more vent tube routed from near the top of the bowls (item #32 in the fiche).   These should route to the same place as the #33 tubes near the swingarm, so they all receive the same pressure, and prevent liquid circulation travel through them (apart from gravity effects).
http://www.westernhillshondayamaha.com/fiche_section_detail.asp?section=2560070&category=Motorcycles&make=Honda&year=1975&fveh=132839

I see your point now, due to lower preassure inside the carbs the air can possibly be sucked in to the carbs. Ill have a check and honestly I didn't knew those hoses Existed. Thank you TwoTired for your allways good inputs !
But itsn't only during movement this happends. Also after standing stil in rain or washing. So maybe that's talking against the carbs, but Ill def. have a look.

What are the electrical connections you have down there hidden behind the vent tubes? Looks like those would get wet in a hurry. I hope they aren't the wires going down to the points.

I don't think they are of any importence. If I remember correctly I started the bike after the engine had been out without connecting them. BUT every possibility is a possibility so Im def. going to check them out, and make sure that they doesn't provide anythink critical. Thanks man !

Did you take your spark plug wires apart and check them?  I used to have a lot of problems in the wet weather until I pulled the plug caps off, cleaned up the connections and packed them with dielectric grease before re-assembly.  I think water was getting into the caps and causing problems. 

Some of the spark plug caps was cut, and re-connected due to bad connection (she was running on 3 cylinders). I haven't used the grease tho, but the idea has striked me sometimes is there any special brand, or just dielectric ?






AS for an update. I gave her Quite the "water treatment" while running, she didnt die. Then I washed her really good, dried her with compressed air, she wasn't that happy. She started right upp but didn't go on all cylinders. When touching the number 1 cylinder, I got an electric shock. LAter that evening (a few hours) and noticed the little "spark arch".

Make it rain baby !
Make it rain

Little spark arch.
Cb750 spark arch



The day after she ran great again, and have been doing so the last days. Forward to this morning. I drove home (60 km) from work after a night shift - She ran great. Parked her and since she was still warm I didn't put on the "rain poncho", during my sleep it started to rain quite hard. A hour ago I tried to start her. This is what happens.
-Starts right up
-She's cold and dont want to rev. Normal
- I notice after a 20-30 seconds that se doesn't rev above like 2000 rpm. I start to film
(this is what you see in the film)
- I rev her up, only time it worked
-next times I TRY to rev her up but the engine dies, stall. To be clear, I DONT release the throttle.
- can't rev, engine dies.
- start right up, can't rev engine dies.
-Won't start anymore.
Water water water


I bet in a day She'll be running great.

[Black 750K8]

Well you are pissing uphill until you fix that spark leak and if you have one you might have others you have not seen yet get that sorted

[reddyvv]

Very true!

If those are the original resistor caps check the resistance to make sure they are in spec. Too high a resistance will cause the spark to jump to the engine rather than continue on to the plug.

Also, are you using the right combination of resistor caps and/or plugs?

[Viktor.J]

Well you are pissing uphill until you fix that spark leak and if you have one you might have others you have not seen yet get that sorted

Not sure ehat you mean.
To be clear, that spark arch is only occuring in combination of water. The bike runs great otherwhise.

[2wheels]

So, I have not read every post in this thread, sorry.
But I thought the idea of water being sucked up the overflow pipes was interesting.
Water would not be sucked up if the vent pipe was clear, not blocked.  If it is blocked or clogged then maybe.

I have attached a picture of my carb vent pipe.  I have pulled it out so it can be seen.  Normally is tucked in.
Good luck with a very interesting problem.

[TwoTired]

You really shouldn't get a shock by touching the wet engine.  Maybe the spark leads themselves.  But, not the engine cylinder.

Can you see the arcing in a darkened garage?  Being able so see it, might allow you find where the spark leak is.  Cracked insulation would have to be replaced.  And one crack is all it takes to shunt the spark current.   But, you might also have to coat all the connection points with pure silicone grease.  Next, look carefully where the coil mounts.  If it arcs to the frame there, at least two cylinders will quit.  The spark energy does travel through the head between spark plugs.  If it is taking a short cut from engine to frame back to coil, one plug wouldn't fire of the pair.

Silicone grease will prevent and repel water contacting the electrical conductors, as well as the formation of a water electrical pathway.

A thought.  Spray the wire leads with silicone spray when dry.

I wonder.  The spark plug boots have a rubber seal between wire and boot and another between boot and spark plug.  Do your boots still have these?  Or, were they lost in the 30+ years since new?

[Viktor.J]

You really shouldn't get a shock by touching the wet engine.  Maybe the spark leads themselves.  But, not the engine cylinder.

Can you see the arcing in a darkened garage?  Being able so see it, might allow you find where the spark leak is.  Cracked insulation would have to be replaced.  And one crack is all it takes to shunt the spark current.   But, you might also have to coat all the connection points with pure silicone grease.  Next, look carefully where the coil mounts.  If it arcs to the frame there, at least two cylinders will quit.  The spark energy does travel through the head between spark plugs.  If it is taking a short cut from engine to frame back to coil, one plug wouldn't fire of the pair.

Silicone grease will prevent and repel water contacting the electrical conductors, as well as the formation of a water electrical pathway.

A thought.  Spray the wire leads with silicone spray when dry.

I wonder.  The spark plug boots have a rubber seal between wire and boot and another between boot and spark plug.  Do your boots still have these?  Or, were they lost in the 30+ years since new?

Now, like 3-4 hours later then when the engine didn't start after the "cant rev more" She fired right up. Rev happily and normal.
Rev normal

But still, eventhough she runs normal I got some chocks from the caps, and this is what I found when moving the cap closer to the cylinders.
Caps arch
ARCH..... Hmppffff.... !?!?!

There might be that I have to take back what I said beafore. Is it possible to ride the bike normal, even though something is obviously wrong ?

And most imoportant, by changing the coils, ignition cables, plug cap you think this problem would go away ?
Cause im not that interested of a quick fix, I rather change it and ride safe.