'85 Yamaha XJ700 Intake Manifold Air Leak

I am having a problem getting 1 & 2 to fire. I have spark so it is not the coils? On a previous thread I got a suggestion there could be an air leak on the intake manifold. I have tried previously on other older Yamaha's to remove the manifolds and this can be a real problem after 30 years. What still concerns me is that this is a real coincidence of having the same issue with two cylinders ie 1 & 2? I read on a thread that one could use RTV Sealant to just seal the connections. I have also used Plastic Dip on the actual boots.
What is RTV Sealant and what name do I use to purchase it at an auto parts store??
I also today checked the compression and am getting ~150 on all four cylinders. I have also removed the carbs twice, cleaned twice, set the floats to ~16mm dry and bread tied the butterflys. Again the two cylinder coincidence is still got me questioning the problem causing two to not fire? About to do the carbs one more time?
gene still in the Tampa area of FL

 

Unscrew the plug caps and cut the wires back about 1/4 ", then screw the caps back on. See if she fires 1&2 then. You also might want to check the condition of the plug wires by starting her up in a very dark place. You may see a light show.

 

I did as you suggested and got good spark on all four. Perhaps even a bit better than before but still not firing on 1 & 2.
I also tried and was able to remove all four carb. manifold boots. The allen bolts actually loosened fairly easily to my surprise.
What type of gasket material is best to be used?? I can and will cut four new gaskets and apply gasket sealant and hopefully reduce/eliminate any possible air leaks.

 

Chacal sells reproduction and OEM gaskets. If you're cutting your own just use a standard gasket paper (not too thick). If you are a cheapskate you can use a cereal box. Go ahead and clean the carb boots and check for cracks. They can be filled with black RTV, or even cover the whole of the outside of the boots. Some people have cut bicycle innertubes and used htem as an outer layer over the RTV. Self amalgamating tape is another option to help seal any craks in the boots. I've used that stuff sucessfully to patch vacuum material handling systems that run 2" HG vacuum (though I will confess to mostly using aluminum cans and duct tape for that purpose).

 

I used standard paper gasket material and no gasket sealant. It's been about 2 years and I've had no problems at all.

My manifolds are in perfect shape and hopefully will stay that way. However, if I needed to repair cracks in them I would use rubber sealant to fill the cracks and then either inner tubes or heat shrink tubing. I play tennis and just ordered heat shrink grip sleeves to enlarge the grips. They are slightly less than 6 inches in circumference and easily shrink to the tennis grip size, and as they shrink they actually get thicker. I haven't measured the manifolds but if they are less than 6 inches in circumference I would sure give the sleeves a try. They are only $2.00 each and are about 10 inches long so 2 would be more than enough. They are available on Amazon, Ebay, and from tennis supply shops.

 

seems to me if you got spark, but it's not firing.....then you gotta first look at a fuel starvation issue.

 

I just saw a set of 4 boot on eBay for like $25 I am 99% sure they were for your bike