Viton Float Valves for older carbs

[egsols]

Thanks 81xsproject,

I take it then, that you didn't have to bend the tang very much? When I put a viton tip valve in the 79 seat the float went from ~25.7mm to over 31mm.

If I use the xv920 setup with my 80/81 plastic floats do I set them at 25. 7mm for the 79 or do I go to the lower setting of ~23 for the 80 or do I trial and error it?

[81xsproject]

Check out THIS. From the test that I did it should be very close to the same.

[egsols]

That's what I was thinking,

Thanks 81xsproject, good work!

I'll let you know how I make out.

[egsols]

I finally got time to try out the 920 valves and seats.

I used the fibre washers and my stock brass floats and did away with the clip.

Had the floats originally set at 25.7mm but when bench tested they overflowed.

Went up 2 mm and the tube method showed the fuel about 3 mm below the top of the bowl.

Dropped 1 mm and they started to overflow again so for me it seems that 27.7mm is the best setting.

I synced them and took a quick run, everything seems dry so far. Keeping fingers crossed.

I also think they were hanging up a bit when fully dropped so I set the drop at about 31mm.

I need to go for an extended run, though. The seats are marked 1.4 with the stock ones marked 2.0 so there is a difference in the feed hole, the 920's being smaller. I did note that you said at WOT you had no issues and I haven't noted any yet either but haven't had a chance to go WOT.

[81xsproject]

That is odd. All the ones I bought had the 2.0 seats. And, I bet I have bought 16 or 20 of them.

[boyat68]

egsols:

What were your thoughts in doing away with the clips? I thought that the clips were a way of ensuring that the float had positive pull on the valve, preventing wedge capture. However I did find that some of the clips would come loose during my marathon carb cleaning, but I chalked that up to my heavy handed handling of the valves during assembly and disassembly. I replaced them and pinched them back around the valve.

[egsols]

81xsproject,

I just went back and checked the part no.s The seats I ordered are for a 81-83 XV920 are oem part 42H-14390-00. For a XJ750R the OEM numbers are 42H-14390-00 for 84 and 10L-14390-02 for 81-83. I wonder if the 10L part has the 2.0 opening and the 42H has the 1.4 opening. At any rate, when I bench tested with clear line, I let the lines hang done into a gas can and the flow throught the carbs seem pretty good. I'll know for sure when I try WOT. Do you know the OEM number for the ones you have been using?

boyat68,

As I'm using the original brass floats I found the clips to hang up on the edge of the opening for the tab. The 79 set up never had the clips plus I set the total drop to maybe 3mm max so I didn't think the clips would be of much use and could possible cause me more grief.

[81xsproject]

What I found out about the WOT test is that it takes a while. I never had a problem with WOT on one petcock. Never. Until one day I started practicing launches and dragging. Right after I would decide to back off, ~100 mph, I would notice the way the bike was running a little rough and that the AEM showed a lean mixture. After a couple times if occurred to me that the bike might be starving and opened the second petcock. I tried again with both and no starvation. Doing long WOT tests is hard to do on the XS if your not at the track

[egsols]

I'm at a stage in my life where a long periods of WOT are no longer required. Just want to know I have the option.

One petcock? Are your lines teed?

I had it out for a ride last night. Took it up to 8500 using about half throttle. No hesitation, no flat spots. Couldn't really get out to the open road, I had my 9 year old on the back, but I ran it in second around 5000 and gave it a few shots. Seems to run really smooth through all revs.

So far I haven't noticed a difference between the 1.4 and 2.0 seats but time will tell. Still need to do a chop to check mixture. Its popping lots on decel, but with the 4 into 1s, I think that's the norm.

[egsols]

Status

All appears good, I have noticed any leaks yet.

The new float valves and seats seem be doing their job. (BTW Used the brass floats adjusted to 27.7mm)

I went for a ride last night again and had a small chance to get on it. I don't think the smaller seats are restricting the fuel. No hesitations whatsover under heavy acceleration. The only weird thing I noticed was when I gave it hard it would get to about 6500-7000 rpm and then immediately go past 8000 where upon I would shift. It was almost as if the clutch was slipping past 7000. I took it down to about 50k (30 mph) and left in 5th. I gunned it at low revs to see if the clutch would slip and it didn't, the bike just pulled.

I tried it once again, took it up fast to 7000 and again it shot past 8000 right way, but this time I think I felt the rear slide just a bit.

Is the power band on these at that rpm range and are they known to break the rear tire loose within that range?

[TopCatGr58]

Hey Ernie,

The power band is about the 5k + zone. When mine started slipping the clutch it showed up in 4th gear, trying to do some high speed passes, and would show up at the 7K + range, same with 5th.

And unless you have severely worn/slick tires or were hitting an oily section, I've not heard of our bikes being able to break the rear loose at that speed.

T.C.

[egsols]

Hey T.C.,

I was in 1st and 2nd when it shot up after hitting 7K. When it did it, it didn't feel like I was loosing any momentum. That's why I'm not sure if its slipping.

I figured if it is worn it would definitely slip at a slow speed in a high gear under load. Am I right in this assumption?

This 79 definitely has more snot then my old one and has never run better then it does now that I finally have the carbs set up.


BTW my tires are new but were cold at the time.

[TopCatGr58]

Originally posted by egsols
Hey T.C.,

I was in 1st and 2nd when it shot up after hitting 7K. When it did it, it didn't feel like I was loosing any momentum. That's why I'm not sure if its slipping.

I figured if it is worn it would definitely slip at a slow speed in a high gear under load. Am I right in this assumption?

Did you feel any surge in speed/power? Perhaps the tach is sticking and you're just seeing the needle surge/bounce once it revs to that range??

Yes, your assumption is correct, will slip more at lower speeds in higher gears.
T.C.

[egsols]

Its really tough to explain....its such a short period of time from 7k to 8.5k. The power is on real good getting there and I shifted just before redline. As I noticed the needle jump, the engine sound matched the revs. I just have a hard time ascertaining whether its slipping or spinning.

On an earlier test ride I took it up to 8.5k, but under partial throttle, and there was no jump, it only occurs when I'm pretty much WOT. I don't think there are any problems with the tach, I have been watching it closely.

[TopCatGr58]

Sounds like slippage to me!

At that speed I couldn't really feel any loss of momentum either, but I could see the rpms rising but no increase in actual speed!

When was the last time you checked your clutch adjustment at the engine? Got enough slack in the cable, lubed, not sticking?
T.C.