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1984 VT700 problems

6K views 17 replies 4 participants last post by  xtoma 
#1 ·
Ok, i've almost had it with this bike. :frown2:

first of when i bought it I noticed that the bike was missing the airfilter, bought a new one. later the bike left me stranded with a dead battery, so I changed the stator. Later the RR cooked the battery so had to replace that aswell.
The bike was running a little poor when speeding up, not sure about the RPMs because the tachometer was dead(opened up the tach yesterday and noticed the PO tried to repair it. I got it working now though) anyways, took the carbs off to clean them, they were dirty and of course one of the diaphragms were torn. Did a quick fix with a piece of a nitril glove and some superglue and went for a spin, the fix lasted 1 hour. Then the bike started running extremely poor, with a lot of loud backfiring and flames coming out of the exhaust from the rear cylinder. Got the bike home, ordered new diaphragms from JBM Industries, installed them and put the bike back together. I have read a lot of posts on this forum that recommends shimming the needles, so I did that aswell.

Tried starting the bike today, drove it down the road, seemed like the bike was getting to much fuel because it was running poorly and wouldn't rev up. pulled out the spark plug from rear cylinder and it was wet. Front sparks was dry though.
AF screws was 2,5 turns out at this point.
Should I remove the shims from the needles ?

At idle I rev up the engine to 5-6000 rpms and when i let go of the throttle the bike was holding the rpms at around 2000rpms for 3-4 seconds before it went down.
Im thinking maybe the vacuum pistons don't slide good enough ?

When revving up to 5-6000 I got white smoke from rear cylinder exhaust and it's dripping coolant from the hose underneath the bike.
Is this a sign for blown head gasket? I hope not because that seems like an awful job.
Sorry if this post seems long and complicated :grin2:
 
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#2 ·
Sorry to hear of all the problems. Take them one at a time. Take the radiator cap off and start the engine to see if coolant is pushed out of the filler neck. Not just expanding but pushed out forcefully. Maybe coolant getting into that cylinder.
I that is good go after the rich condition for the rear cylinder. Maybe the float is too high for that carb, or not seating the needle valve and flooding the bowl. Maybe the slide is sticking up and running too rich from that. Just adding the shim washers should not effect only one cylinder so badly and not the other the same way.
 
#3 ·
Hi xtoma, One way to confirm if a head gasket is leaking is to use a test kit. I have used this on 2 cars that were over heating and after testing it with a test kit and special fluid, confirmed my suspicions. In both situations, the head gasket was damaged. You can actually get the test kit, from Autozone, for a small fee. That cost is returned to you, when you bring the test kit back. However, the cost of the test fluid will be a cost to you. Here are 2 pictures of the instructions and the test fluid. If the dark blue fluid changes to a yellow color after testing, then exhaust gases are getting into the coolant. Hope this helps. Bob
 

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#4 ·
Hi, I don't have any Autozone nearby her in Norway. I think i'll try the radiator cap test first and go from there.
I checked the oil and it seemed very good. hope I get some time to work on it later ine the week.
But if it comes to a blown head gasket, do I need to take out the engine ?
 
#5 · (Edited)
OK Guys, time for a little update.
-Started by taking the radiator cap off, as swifty2014 recommended.
Tried twisting the cap but it wouldn't nudge, had to take out a little screw (why was it there?)
as you can see on the pic below the cap had some wear and tear.

Time to order a new one?
Took a smell at the cap too, didn't smell like gasoline.
-Turned on the engine and waited 8-10 minutes until the engine was warm and saw the coolant started to rise, no bubbles and it went pretty slow up. I guess it's supposed to do that ? turned off the engine when it reached to the overflow hose though.

-I also checked the engine oil and it didn't seem contaminated, there were also no white rim under the oil cap.


A friend of mine has a compression gauge, will try to get a hand of it in a couple of days.
The ongoing carb issues is due to a later post.

xtoma
 
#6 ·
So, still waiting for the compression tool.
Im beginning to deal with the idea of pulling the engine and replace a head gasket.
I also have some leaking from the chamshaft plugs.
Will it be possible to take the head covers off, seal them with RTV and reuse the plugs ?
 
#7 · (Edited)
So finally got my hand on the compression tester(had to buy one though)
Let the bike warm up until the coolant started to rise to the overflow hose, then pulled one sparkplug out of each cylinder, disconnected all spark plug wires and stucked the tool in.
Took a photo of the smoke coming out of the rear cylinder too.
Can also add that the rear cylinder exhaust pipe didn't get warm compared to the front, but it caughed out white smoke though.


This was the result on the front cylinder (165 PSI)

And this is from the rear cylinder. (140ish PSI)

Something is obviously going on with the rear cylinder. Is the verdict a head gasket change?
I've checked out some gaskets at ebay, but the photos in the shop manual of the gaskets is different then the image of this: Gsk,set Cyln Head Vt700c Shadow 1984 (e) Usa 12250ME9306
Am I missing something here?

Xtoma
 
#8 ·
Does the white smoke smell sweet ( pecan ice cream) then it's probably coolant. But too much fuel, very rich, could be that smoke also but it smells lousy.
If the plugs are wet with gas then it is not coolant. Check that out before tearing it apart. Does the radiator level rise without the cap on when you compression test?

If you have to tear into it, It would probably be better to get the complete set for a head gasket repair, since other gaskets are always involved also.=

Athena Complete Gasket Kit for Honda VT700C Shadow 1984 1987 400210850754 2 P400 | eBay
 
#9 ·
To be honest, the smoke did not smell much. this time the plugs were dry when I took them out.
When i warmed up the bike to do the compression test the radiator cap was off.
So it's not only the head gasket that has to be changed during this operation ?
 
#10 ·
I would do as many test as I could to avoid pulling the engine and tearing it apart. Many times a project is started and parts are hard to find or expensive and it just sits apart for years.
There is a lower gasket on the cylinder assembly also that should be replaced when it is disturbed and smaller O rings and gaskets.
It sounds like it may have been running pretty good at one time? You may have to go backtrack your work and look for carb problems. Or vacuum leaks at the rubber boots.
If the smoke is a little bluish that may be oil burning and the lower compression would fit with that. Mine also burns some oil on the rear cylinder and I can look into the plug hole and see the top of the piston is very clean, no carbon, so it is being cleaned off with oil consumption.
 

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#12 ·
If it rises slowly as it warms up that is normal. The cap allows coolant to expand and go into the reserve tank. Then when it cools down the coolant contracts and flows back into the radiator so it is always full. The smaller rubber seal on the bottom of the rad cap is for the return process with a lightly sprung check valve in the center, that little metal shiny disc. It should lift a little on it's spring.
If the coolant is rising fast and violently then it is a problem.
 
#13 ·
But the coolant is dripping out of the hose under the bike, it's draining the system. The head gasket you refer to in pic nr.1 does not look similiar to the part number i posted. Im a little confused [emoji848]


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#14 ·
Did you check to make sure the overflow line is connected to the expansion tank? It almost sounds to me like it's not and when the bike heats up and the coolant expands it's expanding right onto the ground instead of the tank.
 
#15 ·
Yes, the overflow hose is connected between the radiator cap and the reservoir tank. The dripping coolant is coming out of the drain hose that is connected to the reservoir tank and leads the coolant to the ground.
I need to know if this is a damaged head gasket or not, and what partnumber the correct head gasket has.
damnit! I've only got to ride the bike 4 hours this entire summer :(
 
#16 ·
It sounds like the reserve tank is too full if the coolant is flowing out of the over flow hose that comes out the top of that plastic tank. And the radiator cap rubber seal being broken will contribute to the problem, by not controlling the normal push-pull of the coolant. Get a new cap and make sure the level of coolant inside the reserve tank is not more than 1/2 way up . Try it all again. I don't think you have a head gasket problem at this point.
 
#17 ·
I've done some vacationing since the last post, but had time yesterday to do some work.
Took off the carb again to look at the slides, dried off the WD40 I soaked them with after the rebuild.
Think that did the trick, but I have not had the chance yet to test it other than in idle
the plugs on the rear cylinder were still wet after idling, and the cylinder cold.
took the plugs out for further spark testing and found out that the rear ones were dead.
Crossed the wiring to the CDI boxes and got spark to the rear cylinder but not to the front.
So I concluded that during the last trip the CDI to the rear cylinder died, and maybe worked once in a while since it sometimes backfired when i drove the bike.
And the bikes poor running when i took it home was caused by running on one cylinder.
Just ordered a new(used) CDI igniter on Ebay and are crossing my fingers that the problems with this bike now has come to an end. :)

xtoma
 
#18 · (Edited)
Connected the new CDI I got in the mail today and checked for spark, thumbs up!
But the damn bike still wouldn't start!
Took the carb off for the seventh time to check it out.
Checked the float levels, and they were stock height, took out the jets and cleaned them, again.
noticed that the slow jet tube was a bit clogged in the end were the airsnorkel is mounted.
So i got that cleaned too. reinstalled the the carb and got the same result. At this point I wanted to poor gasoline over the bike and set it on fire.
guess reason kicked in since I didn't do that :p

As a last resort I found my old sparks and put them in, AND IT WORKED! :D
I guess the rear cylinder spark circuit got fried from the bad RR that gave it around 15V since both the CDI and the sparks got damaged.

but, I still got some white smoke from the rear cylinder, it got better after it warmed up abit though. and it backfires a little during decel so I guess A/F mixure is a bit off.

Figured I should keep updating this thread during the progress so it may be of some help to the next poor guy.
 
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