Hello. I have a 1979 cb750K four. I'm in the middle of rebuilding the bike and I'm glad I watched this video - I should replace the throttle/choke shaft seals. However, no kits are available in my area. I was wondering if you could indicate what size the o-rings should be for the throttle shaft and choke shaft. Thank you.

muy buenos todos los consejos...

Thanks for this. It's not the problem I have, but it's always good to cross one more thing off the list.

thanks a lot, very good advises,

that frame looks beastly compared to my 82 nighthawk 650

I realize this is an older video and the bike is long gone but I have some experience in replacing felt throttle shaft seals in these Keihin VB carbs. I too bought seals from motorcyclecarbs.com because I was frustrated with vacuum leaks at the throttle shaft on bikes I did carbs jobs on in my own shop. The seals I got were very flimsy and only worked 50% of the time, same as you, and that frustrated me even more. My solution was to manufacture better seals myself. I learned how felt seals are made, scanned the classifieds for a used punch press, paid a tool and dies shop to make custom cutting dies for my press, researched different felts and finally ended up with a seal that is twice as thick as the originals, made from denser felt and sized so it holds the shaft much better that the original seals Honda used. Here is a link to my seal install video showing in detail how the job is done. kzfaq.info/get/bejne/n5t_eMqWxrG1hnU.html I also sell these seals, and have sold them all over the world. They won't leak if they are installed properly and I have lots of testimonials from satisfied customers.

The gas leak was coming from the accelerator pump, so I assume the gaskets/seal were bad.

Is there a site that you use to find old parts for all bikes i have a 1980 yamaha xj650 maxim. And I cannot find manifold intake boots .I waswondering if they were all the same I seethere is only like two different kinds but are they "interchangeable " to a degree

I have the same model bike. My issue is that it bogs down at top speed around 7000 rpm I have to twist the throttle back and forth to get the speed to accelerate further. Is that a vacuum leak issue or carb jets/pilot?

Great VideoThanks

Loved the steps to test the seals on the carb boots... working on one of these now. I have a question tho, that main vacuum line that goes between carbs 2 and 3, where does that reconnect to? I should have taken notes..lol

Did u change ur caburetor

what was the name of that shop for the master over haul kit?.."brand X".com?..having the same problems..thanks

Hey mate! currently looking for a replacement for the standard carb on my 750 81'. What carbs have you got on that bike? :-) and cheers for the great videos!

Your probably looking at 6-8 labor hours to replace throttle shaft seals. The carbs have to be de-ganged and all butterfly plates removed. Labor rates vary.

hey mate did you sorce boots for the bike ? im just looking for some for mine but no joy

Couldn't you use any liquid that can be sprayed? Why not use a spray bottle with water? I get nervous spraying carb cleaner on my bike, I don't have compressed air to blow it off afterward.

I know I am a little late on this.. but I got an 82 XJ750 myself.. and it doesn't idle unless I give it gas... I know for sure I got a leak in the petcock, but its not terrible, oh and when I give it gas sometimes it sticks open.. aka I pull off the throttle and it stays and climbs until I put load on the engine (pulling off the clutch a little puts the idle back down ) I mean I am guessing that would be an air leak,simply because it doesn't stay high...I tried to retune the carbs but Without the carb tool I did it by ear the best I could .. I am able to ride still, but it is just weird I am sitting at a red light and all of a sudden the idle hypes up and sounds like I am reving.. idk seems like a vacuum problem IMO but just wanted a second opinion .. I might make a video on it later when the weather gets a little warmer

It's the pods dude. These DOHC 4s have constant velocity carburetors. They're not meant to run pods. Part of your vacuum leak is from the lack of airbox. The pods are letting too much air in. That's why you need the choke. You can TRY rejetting, but it will never run as good as stock.

good vid. What would you estimate this would cost to fix if it was brought into a shop?

Google "randakks dohc kit" Contact them and make sure the o-rings for throttle shaft are included, if you have a leak there as well. If not, I can give you a good resource for sizing o-rings.

It's all part of diagnosing problems.

I have an 82 Yamaha XJ-750 Maxim, and it will not idle without Choke. It also seems to be super underpowered at higher RPM's. I've replaced the Carb Boot's, the Valve stem seals checked the rings Adjusted Valve's Cleaned the Jet's. And nothing seems to make a difference. Any theroy's on what I'm dear with are welcome..

thanks, i appreciate the info..the bike i have is a 78 hondamatic, and is sucking WAY too much air,won't run without the clutch up..in your personal/professional opinion, how much would it cost to have a shop fix the problem?

hola tengo km a moto cb 750 y sólo me funcionan dos pistones el 2 y el 3 pero el 1 y el 4 no me funcionan. será o alguien puede ayudarme con un consejo

la moto es del año 1980

You mentioned putting oil on the pod filter. Will that help and why?

the cam chains are dieing., adjust them

Yell at it to get back in the accelerator pump.

there is some things that will only show up if you riding the bike!

No, the owner sold it as is instead of fixing it.

Sounds a wee bit like my 83 cb 1000c, only yours sounds better.

I also had bad luck with replacing the stock seals and since I work on lots of Keihins I decided to manufacture a much improved replacement seal. Here is my vid showing how to do the seal replacement. kzfaq.info/get/bejne/n5t_eMqWxrG1hnU.html