Carbs - syncing and vacuum leak.

[KIC]

So I started looking for my proverbial gas smell on my 89. Couldn't find anything wet or seeping. Decided to sync the carbs. I also checked the vacuum caps that I had to remove to hook up the sync hoses. I checked them by sucking on them and letting them stick to my lip.

 

The last one I checked would not create suction. I could not find a crack, or leak, but it would not create suction. So, I replaced it with one off of the 87. after syncing and the new cap, boy...it runs smooth.

 

Here is the question:

 

When syncing the 89, the Carbtune reading was close to 32 on the scale. Is there a level/reading that it should be ? What/how is that adjusted ? I was able to balance the carbs and the sides.

 

I was also playing with my 87 and even though I still have major carb issues on that one, The reading was around 20 on the scale. Now I know that the 87 could, and probably is not an accurate reading due to the carb issues, but it got me thinking about the readings.

 

[GolfVenture]

Thanks for the idea of testing the vacume caps, for my 89 VR runs ruff.

[saddlebum]

I had the same issue with my vacume caps, all of them were cracked. It was on a sunday so I replaced them with pieces of vacum hose then plugged the hose with little steel balls. I did make sure they were to big to suck int the carbs first though.

[frankd]

Bill,

 

The port rubber plugs on my 89 have dried out and cracked, and after 3 years the replacements have cracked also. In fact.....this morning, Barb and I rode to J.C. Whitney's to pick up a set of rain boots, and stopped for lunch. When we came out, the bike backfired when I started it. On the way home, I noticed that the idle was a bit low, and the one cylinder dropped out when you took off, and then came back to life when you hit the throttle somewhat. I just installed new diaphragms and set up the carbs, so I figured I had one of the idle mixtures set a bit lean. Well, I pulled the sidecovers and found that one of the rubber plugs was missing---it blew off when the bike backfired. The brass port measures 5mm or .200". At Advance Auto and Autozone, they don't carry 3/16" Rubber plugs. I went to O'Reily's and they had 3/16" Doorman plugs. The last time I bought them at Pep Boys. Now, my 83 with 140,000 miles on it is still on the originals, and they are still in good shape. I guess the Mk II bikes get a bit hotter with the side covers closed. I'll bet they get a lot hotter in Arizona.

 

You asked about the vacuum readings....I don't have a Carbtune, so I have no idea what scale it uses. My antique vacuum gauge setup indicates a little over 10" of mercury on my 89, and about 9.5" on my 83. I did find a conversion web site, and it gave the following...

 

10.25 inch of mercury [0 °C] = 34.710 483 834 kilonewton/square meter

OR

 

32 kilonewton/square meter = 9.449 594 582 8 inch of mercury [0 °C]

 

I set mine @ 1000 RPM

 

 

Frank D.

[KIC]

Funny thing is that the caps that looked cracked and old were holding suction. The one that looked good, no cracks didn't. I still do not know why.

 

I need to find some new thick/heavy duty caps for both bikes. Bought some others in a package, but they seem flimsy and I'm not sure they could handle the heat.

[Snaggletooth]

Bought some others in a package, but they seem flimsy and I'm not sure they could handle the heat.

 

I've tried the packaged vac caps to. Waste of time. As soon as the motor heats up they are worthless.

 

I like the idea of the heavy fuel line and plugging them with ball bearings. Next trick to try.

 

Mike

[KIC]

Bill,

 

The port rubber plugs on my 89 have dried out and cracked, and after 3 years the replacements have cracked also. In fact.....this morning, Barb and I rode to J.C. Whitney's to pick up a set of rain boots, and stopped for lunch. When we came out, the bike backfired when I started it. On the way home, I noticed that the idle was a bit low, and the one cylinder dropped out when you took off, and then came back to life when you hit the throttle somewhat. I just installed new diaphragms and set up the carbs, so I figured I had one of the idle mixtures set a bit lean. Well, I pulled the sidecovers and found that one of the rubber plugs was missing---it blew off when the bike backfired. The brass port measures 5mm or .200". At Advance Auto and Autozone, they don't carry 3/16" Rubber plugs. I went to O'Reily's and they had 3/16" Doorman plugs. The last time I bought them at Pep Boys. Now, my 83 with 140,000 miles on it is still on the originals, and they are still in good shape. I guess the Mk II bikes get a bit hotter with the side covers closed. I'll bet they get a lot hotter in Arizona.

 

You asked about the vacuum readings....I don't have a Carbtune, so I have no idea what scale it uses. My antique vacuum gauge setup indicates a little over 10" of mercury on my 89, and about 9.5" on my 83. I did find a conversion web site, and it gave the following...

 

10.25 inch of mercury [0 °C] = 34.710 483 834 kilonewton/square meter

OR

 

32 kilonewton/square meter = 9.449 594 582 8 inch of mercury [0 °C]

 

I set mine @ 1000 RPM

 

Frank D.

 

Thanks for the info. Guess I will have to pull the Carbtune and do the math to see if that works out. I'll try Orielly's..that is where I bought a package, but they are flimsy and thin. I'll stop by PepBoys too. Probably go to a local Hot Rod shop and see what they have.

 

Things do get hot out here ...but like they say ...It's a dry heat....

 

Thanks Frank.

[jdross440]

I saw on a post here somewhere that Kawasaki sells the plugs for less than half what Yamaha wants for them. The vacuum hose trick is much cheaper though. A short 3/16 screw with some RTV will work in the place of the ball bearings and won't get sucked into the engine.