1984 700 LTD, Rough Idle.

[gofastbobby]

Hey guys,

First things first. Great Site. I have already learned a lot about the 84 700 LTD I purchased last week. It's a nice bike for the few dollars I had to give for it. It has a 17,000 miles on it and from what I can tell has been very well maintained for most of it's life, with the exception of the last owner. She only bought it for riding around her yard, SMH.

I have a few issues with it that I have learned about so far. First I'd like to address is the rough idle. It's very cold blooded, especially at the beginning of the day. When I leave for work it's only about 50 degrees and doesn't want to idle without choke for about 10-15 minutes of riding. Once it's warmed up it idles at around 1500 rpm's, but misses on at least one of the cylinders.

It doesn't currently leak fuel, that I have been able to notice, from the petcock or carbs. Also, this is the first week I have ridden it on the road, still burning the first tank of gas that I put in it.

My plan of action is new plugs/oil&filter/air filter and an inline fuel filter. That should make sure the problem doesn't get worse.

Beyond that how should I tackle this rough idle problem?

Thanks,

--Bob

[MFolks]

Fresh, properly gapped sparkplugs?Fresh gas? Checked the compression? Checked the valve clearances? Got a shop manual? Look here:

Manuals (Some of these websites sell used manuals, just ask)
Repair Manual | Owners Manual | Haynes Repair Manual | RepairManual.com
ManualsNMore.com: Factory Service Motorcycle & Auto Repair Manuals
http://www.midwestmanuals.com/
Books4Cars.com - Every Repair Manual, Service Manual, Owners Manual and Book for your Car, Truck and Motorcycle
RepairManualClub Download Area
Motorcycles maluals
Vintage and classic motorcycle manuals and literature

[Hugojose]

Don't expect to get a bike this old and simply ride it with no isssues. It probably needs some tender care.

Yes, all the things you mentioned are required, but I'd also inspect, clean/refresh carbs, check floats, and synchronize them. Synch'ing contributes to smooth the idle. Coils may be an issue if changing plugs do not cure the missing cyl.

At some point you may consider also checking valve clearances, as you don't know if has ever been performed. All air cooled engines are 'cold blooded' as they don't have water jackets to hold the warm, although it should idle low without choke in about 5 mins.

[gofastbobby]

Don't expect to get a bike this old and simply ride it with no isssues. It probably needs some tender care.

Yes, all the things you mentioned are required, but I'd also inspect, clean/refresh carbs, check floats, and synchronize them. Synch'ing contributes to smooth the idle. Coils may be an issue if changing plugs do not cure the missing cyl.

At some point you may consider also checking valve clearances, as you don't know if has ever been performed. All air cooled engines are 'cold blooded' as they don't have water jackets to hold the warm, although it should idle low without choke in about 5 mins.

You are absolutely right about the maintenance. It never ceases to amaze me some of the creative engineering thats found on vintage bikes and old cars.

I worked it over today and found mostly good news. the compression test came out at 120-125. These are the old plugs. Passengers side on the left, drivers on the right in order. The cylinder thats not firing is second one in on the left. I checked the gap of the old ones coming out they were all around .040". I set the new plugs at .030"





After changing the oil and filter I decided to change the air filter as well. The only problem is there was no air filter in the bike, LOL. After getting the compression test done, the new plugs gapped and installed, the oil and filter changed and adding the air filter I took it around the block and it acted maybe a hair better, but mostly the same.

I must say, so far I am very happy with my purchase. With the exception of the air filter, it seems to be very well maintained.

I am hearing the general consensus of cleaning and syncing the carbs, and checking the valves as the next steps. Is there anything else I should be looking in to?

[MFolks]

Maybe now ignition coils and sparkplug wires as your's are probably original. Popular replacements are the 3 ohm coils from Dyna and Accel.
I'd get the copper wired type sparkplug wires rather than the supression ones for greater spark energy.

[gofastbobby]

Maybe now ignition coils and sparkplug wires as your's are probably original. Popular replacements are the 3 ohm coils from Dyna and Accel.
I'd get the copper wired type sparkplug wires rather than the supression ones for greater spark energy.

I just re read my original post and noticed a misleading comment. It only misses at low RPM's, less than 2000. Aside from that it runs well and on all four.

[twoisbest]

Since you have no maintenance history, checking the valves should be a priorty. Checking valve clearance should happen before card sync. Hope you enjoy the bike.

[kawpaul]

Lol at passenger's side driver's side on a motorcycle.

[kawpaul]

I just re read my original post and noticed a misleading comment. It only misses at low RPM's, less than 2000. Aside from that it runs well and on all four.

What he said. vvv

Since you have no maintenance history, checking the valves should be a priorty. Checking valve clearance should happen before card sync. Hope you enjoy the bike.

Missing at low speed is often due to a tight valve on one cylinder where it is not closing all the way. At higher speeds the pressure does not have time to excape and you get ignition.

[zoro]

After viewing the photos of the plugs and the comment made of no air filter, that bikes WAY too lean! Thats why it only runs with the choke on. Get an air filter in it and check valve clearances! Change out the in-line fuel filter too, and if it dont have one, PUT ONE IN IT! That motor needs more gas or less air! Dont mess with the carbs UNTIL you have verified proper valve clearances! Welcome to the forum!

[gofastbobby]

What he said. vvv

Missing at low speed is often due to a tight valve on one cylinder where it is not closing all the way. At higher speeds the pressure does not have time to excape and you get ignition.

After viewing the photos of the plugs and the comment made of no air filter, that bikes WAY too lean! Thats why it only runs with the choke on. Get an air filter in it and check valve clearances! Change out the in-line fuel filter too, and if it dont have one, PUT ONE IN IT! That motor needs more gas or less air! Dont mess with the carbs UNTIL you have verified proper valve clearances! Welcome to the forum!

That's great info. Thank you. The air and fuel filters have been added.

I have not checked valve clearance on a bike before, but am condifent in my mechanical ability. I need a service manual , Is it worth getting the factory service manual?


I also got around to changing the oil in the rear end. That looked really bad. I replaced it with amsoil 80w-90. The aluminum case around the rear gear gets noticeably warm/hot. I first noticed it when I stopped for gas saturday after riding 50 miles or so. Is this heat a normal thing for a shaft drive bike?

I also got my nephew on the bike for a few minutes today, it was his first ride.

[martin-csr]

..

[zoro]

That's great info. Thank you. The air and fuel filters have been added.

I have not checked valve clearance on a bike before, but am condifent in my mechanical ability. I need a service manual , Is it worth getting the factory service manual?


I also got around to changing the oil in the rear end. That looked really bad. I replaced it with amsoil 80w-90. The aluminum case around the rear gear gets noticeably warm/hot. I first noticed it when I stopped for gas saturday after riding 50 miles or so. Is this heat a normal thing for a shaft drive bike?

I also got my nephew on the bike for a few minutes today, it was his first ride.

Awesome! He'll remember that ride and his favorite uncle for the rest of his life! Do get the "factory" manual when the opportunity presents itself, until then, a Haynes or Clymers will do. I run synthetic gear lube in my rear diff for the simple fact that the synthetics withstand the heat more readily than common lubes. My rear diff does get hot. I ran synthetic oil in the motor until this year because Ive come to the conclusion that it just wasnt necessary especially when you change oil every 1000 miles and at $11 a quart its not economical either. I use Rottella T 15w40 with 1/2 a bottle of STP Oil Treatment in the "blue bottle". The STP has "zinc dialkyldithiophosphate" which is a VERY necessary ingredient in older flat tappet and flat lobed cammed engines. There are zinc additives on the shelf but are very expensive, the STP is the same thing at a fraction of the cost. I use "SeaFoam" in the fuel tank to keep the carbs clean and to stabilize the fuel over the winter months. Your bike looks great!

[gofastbobby]

Awesome! He'll remember that ride and his favorite uncle for the rest of his life! Do get the "factory" manual when the opportunity presents itself, until then, a Haynes or Clymers will do. I run synthetic gear lube in my rear diff for the simple fact that the synthetics withstand the heat more readily than common lubes. My rear diff does get hot. I ran synthetic oil in the motor until this year because Ive come to the conclusion that it just wasnt necessary especially when you change oil every 1000 miles and at $11 a quart its not economical either. I use Rottella T 15w40 with 1/2 a bottle of STP Oil Treatment in the "blue bottle". The STP has "zinc dialkyldithiophosphate" which is a VERY necessary ingredient in older flat tappet and flat lobed cammed engines. There are zinc additives on the shelf but are very expensive, the STP is the same thing at a fraction of the cost. I use "SeaFoam" in the fuel tank to keep the carbs clean and to stabilize the fuel over the winter months. Your bike looks great!

Does the Zinc Additive mess with the clutches at all?

Thanks for the advice it's much appreciated!

[Gary - K7GLD]

Does the Zinc Additive mess with the clutches at all?

Thanks for the advice it's much appreciated!

Yeah - I'm a bit surprised at the successful use of STP too - I'm a fan and user of STP - have been or MANY years. but would be wary of it's slipperiness where bike clutches are concerned...

[gofastbobby]

PS: the cylinders, spark plugs, etc are numbered 1-2-3-4 left-to-right as you are sitting on the bike.

Thank You.

[LTD fan]

I also got my nephew on the bike for a few minutes today, it was his first ride.

And i'm sure it won't be his last. You just got a future biker started.

Do get the "factory" manual when the opportunity presents itself, until then, a Haynes or Clymers will do

To my knowledge Haynes or Clymers do NOT have a book for the Zn700. I have the same bike and have looked. Get the factory manual from ebay. There are plenty to choose from there and fairly cheap. It's red/white with a pic of a 750 Spectre on the cover. Part# 99924-1035-03


Take your pick...
750 shaft kawasaki service manual | eBay

[zoro]

Does the Zinc Additive mess with the clutches at all?

Thanks for the advice it's much appreciated!

Short answer, "No!"...When these bikes were built they were engineered for oils containing "zinc"...Through out the years and thanks to the EPA and state emissions standards the zinc has been removed from "most" motor oils. Its the zinc in motor oils and the lead in the fuel that clogs catalytic converters. The few motor oils that still use zinc (at reduced levels) are the diesel engine oils such as Shell's Rotella T and Mobil's Delvac 1300. Zinc and "ZDDP" are "Anti Wear Agents" and not to be confused with "Anti Friction" additives such as Teflon. I used Mobil 1 4-T Racing Oil for years in my bike for 1. It has the highest content of zinc, and 2. Synthetic oils withstand heat and resist thermal breakdown more readily than standard Dino oils. But as Ive already noted, the Mobil 1 synthetic racing oil has priced themselves out of my range of daily use! Ive opted for the Rotella T that indicated 200ppm more zinc than Delvac. Im on my second crankcase full of Rotella T with 8oz of STP per oil change. I push my bike HARD and race it often! Ive yet to slip a plate in that factory clutch and I'm still running factory springs! You must change oil OFTEN if your going to use Dino oils and especially with ZDDP additives! These clutches are engineered to function in zinc bearing oils! I don't run suppressors in my plug wires and I don't run baffles in my pipes! But you can bet I'll be running zinc in my oil! Please, do your own research and feel free to ask me why and correct me when I'm wrong. I have a son that builds and races his own stock cars and engines, and Ive been building and racing cars, trucks and bikes since I was a teenager. "just sayin"

[kawpaul]

Awesome! He'll remember that ride and his favorite uncle for the rest of his life! Do get the "factory" manual when the opportunity presents itself, until then, a Haynes or Clymers will do. I run synthetic gear lube in my rear diff for the simple fact that the synthetics withstand the heat more readily than common lubes. My rear diff does get hot. I ran synthetic oil in the motor until this year because Ive come to the conclusion that it just wasnt necessary especially when you change oil every 1000 miles and at $11 a quart its not economical either. I use Rottella T 15w40 with 1/2 a bottle of STP Oil Treatment in the "blue bottle". The STP has "zinc dialkyldithiophosphate" which is a VERY necessary ingredient in older flat tappet and flat lobed cammed engines. There are zinc additives on the shelf but are very expensive, the STP is the same thing at a fraction of the cost. I use "SeaFoam" in the fuel tank to keep the carbs clean and to stabilize the fuel over the winter months. Your bike looks great!

Most likely turned him into a future motorcyclist to boot. My two grandsons hit me up for rides every time I have the bike around them. The oldest turns 3 in sept and his brother turns 2 in nov. I gave the eldest a ride when he was barely a year old and he has been crazy about motorcycles every since. He would even bug me to watch them on youtube.