tuning and syncing the 4 carburetors on a 400cc inline 4

[montereyjp]

I am looking for anyone who can tune and sync the carburetors on my 1996 Yamaha Diversion 400... The bike is running but sluggish off the line and cuts out a little until 6000 then it smooths out and runs really well up to the redline. So if anyone can recommend a mechanic or a DIY person including yourself if you have the skills that would be great and highly appreciated... I live just outside of Pattaya so anyone here or in the Chonburi province or the Bangkok area would be best but will take it just about anywhere in Thailand to get bike running in top form..

TIA

[montereyjp]

Here is a pic of the bike..

[Richard-BKK]

You need to buy an "universal carburetor synchronizer kit" which will cost you about 3 to 4000 THB on ebay, and the good thing is (if you not break anything) you can sell it again for the same price....

[ll2]

I know some shops specialize on these 400 cc japanese bikes but all of them in Bangkok. With proper maintenance these bikes can go long time!

[montereyjp]

I used to live in Bangkok and I did have it serviced there a couple of times. And yes I agree these Japanese inline 4's can last a long time and it states in the Haynes manual that this peticuluar bike is a mechanics dream... If you don't mind PM me your llst of mechanics who can tune these types of bikes with your number one recombination stated.. If I can't find one closer I will take to Bangkok...

[Dutchbike]

This is how those ( old school) synchronizer kits look like, a shop should have one of these ( there are also digital ones) if not walk away.

I've red that Red Baron BKK is has good mechanics, but also red you have to pay a fee ( if you not bought a bike from them) to become a customer? good luck.

[ll2]

I used to live in Bangkok and I did have it serviced there a couple of times. And yes I agree these Japanese inline 4's can last a long time and it states in the Haynes manual that this peticuluar bike is a mechanics dream... If you don't mind PM me your llst of mechanics who can tune these types of bikes with your number one recombination stated.. If I can't find one closer I will take to Bangkok...

this section of the Charan Sanitwong Road has three shops for years specialized on 4 cylinder honda cb400, yamaha 400 cc and suzuki inazuma 400cc.

I am sure they can help but check before going there as you never know in Thailand.

https://www.google.co.th/maps/dir/13.741508,100.4704521/13.7528533,100.4693965/@13.7542393,100.4688815,16z/data=!4m3!4m2!1m0!1m0

Edited September 18, 2014 by ll2

[Overandout]

This is how those ( old school) synchronizer kits look like, a shop should have one of these ( there are also digital ones) if not walk away.

I've red that Red Baron BKK is has good mechanics, but also red you have to pay a fee ( if you not bought a bike from them) to become a customer? good luck.

synchro set 2.jpgsynchro set.jpgSyncronizer set.jpg

The dial gauges in the pictures are OK, and as you say are "old school" and quite difficult to read.

If you are going to buy a set, the vertical column gauges are better and easier to use.

Also, for the OP, your bike being a Yamaha of the age that it is, your cylinders are almost certainly balanced in pairs, (first you balance 1 & 2, then 3 & 4, then 1/2 & 3/4) a distinct advantage for the home mechanic as you can, in theory, do this with a double gauge rather than a quadruple as shown in Dutchbike's pictures.

If you get really stuck, give me a shout as I can do this for you, but I'm in BKK anyway....

[Kwasaki]

It's an easy job if you know I never used gauges just simple leveling of all 4 carbs will do the trick, so just go to one of the many bikes shop around Pattaya.

[BSJ]

It's an easy job if you know I never used gauges just simple leveling of all 4 carbs will do the trick, so just go to one of the many bikes shop around Pattaya.

What! Explain further please?

[montereyjp]

Hmm the many bike shops around Pattaya all seem to specialize in scooters. I have been to three big bike shops in Pattaya, Road Machine on 3rd road, another one further up past Pattaya Tai on your left as you head towards Jomtien, and the one off of Sukhumvit on a little soi ran by a Thai Hippie guy.. But only to buy parts as they just don't project an image of a professional shop... I guess I could ask if any of these shops own a set of vacuum gauges and if they did I would take the bike there... I have seen a few youtube videos of guys using homemade vacuum gauges that look easy enough to construct but I don't have the vacuum fitting adapters for the carbs.. I don't think I want to attempt the synchronization without the adapters...

Overandout is correct as the carbs are setup exactly has he described. I have the Haynes Manual so have included some pics for your enjoyment.. According to the manual you should sync before messing with the fuel air mixture... Any advice on this would be appreciated.. I am about ready to attempt this myself if I can find the adaptors... Do you think if I took the picture of the adaptors to the shops around town one might have the adaptors for purchase? Would the bleed valves used on the hydraulic brakes work? Btw, Thanks for the offer to help.. Will PM you if I need the help..

[Overandout]

My guess is that by balancing / synchronising the throttles you won't have to touch the mixture.

Also I'd be surprised if you need any adaptors for the gauges, usually there are stubs on the throttles with rubber caps on them which plug into the gauge tubes.

I've used my gauges on several bikes, Kawasaki / Yamaha / Suzuki and never needed any adaptors.

[liddelljohn]

get yourself a Morgan Carbtune it comes with 2 size adaptors ans is more accurate than vacuum guages ,, i use mine on ducatis, suzukis and many other bikes

[Overandout]

Thats the one I've got but I couldn't remember the name!

Sent from a telephone, which make and model is no concern of yours….

[Kwasaki]

It's an easy job if you know I never used gauges just simple leveling of all 4 carbs will do the trick, so just go to one of the many bikes shop around Pattaya.

What! Explain further please?

Before computers and never had gauges use to do it on Kawasaki Z650 and Honda CB400, can be seen as a fiddly job if you have never done it but take the 4 carbs out put on workbench strip down and clean everything and check to see if any of the floats are leaking etc, adjust all float levels to the height required so they exactly the same, put back and carry out adjustments.

I am not saying to use gauges is not a better way, just makes tuning easier.

Gauges or no gauges carbs have to be stripped down and cleaned at some stage.

[Kwasaki]

I think this guy explains things well for the layman who want to know things.

There's several and one about the sync of carbs.

[yankee99]

I can tell you road machine has a synchronizer. I cant say if they know how to use it. I built my own here using aquarium hoses which worked fine. Im not familiar with your bike but on my cbr synching only affects the idle.

I would inspect the plugs before i did anything. You may have a simple vacuum leak.

[montereyjp]

I can tell you road machine has a synchronizer. I cant say if they know how to use it. I built my own here using aquarium hoses which worked fine. Im not familiar with your bike but on my cbr synching only affects the idle.

I would inspect the plugs before i did anything. You may have a simple vacuum leak.

I was in there about a week ago to buy new fuel line for Yamaha, the place seems neglected these days... I had to get one of the mechanics to hunt down the fuel line for me.. They have a bunch of big bikes for sale but there was no one in the showroom..

Do you or anyone have any experience with the next big bike shop further down the road? I don't know the name but it is after Tony's but before the next stop light as you head towards BaliHi.. A young looking chubby guy seems to run the place as I have purchased pieces and parts there before including the universal electric fuel pump that I installed in place of the stock vacuum fuel pump..

It could be a vacuum leak but it idles fine from a cold start but will drift high after it gets warmed up but it remains steady as in not jumping around... I will check the rubber manifolds on the output side of the carbs later today...