Can't get it started

[jim328]

I bought the bike (xz400) as non runner. I stripped and dipped the carbs, sealed the manifolds with liquid tape. Put in new spark plugs and sealed the YICS box which fell apart when i undid the screws. Fitted uniflow filter, put some fresh fuel in the tank and with a new battery the bike started easily and ran well except for idle which was all over the place. There was a serious exhaust leak where the connector from the rear cylinder meets the connector box. I rode the bike for 6kms and it ran fine expect for the idle and exhaust leak.

So the next day I reassembled exhaust system and sealed the joins. Bike would not start. Not even a hint of a spark. No matter what throttle setting or choke setting nothing happened. I tried spraying engine start down carbs and it would start straight away then stop a few seconds later. Spark plugs are always dry so its not flooding.

So I tooks carbs off again, stripped them right down like last time and dipped again. Then used a whole can of carb cleaner though all jets, holes, practically every part got liberally sprayed. Then I used compressed air to do the same thing. The float chambers were full of fuel when I dismantled them and the float heights are set correctly. I put them back on bike,, went through everything but it still won't start. I am ready to give up. Does anyone have any idea what could be wrong?

[Night Vision]

sounds like you cleaned the piss out of the carbs
put some piss back in!  ::)

when you cleaned the carbs, do you separate them? have you eyeballed the sync to get the butterflys close to open evenly?

[Tiger]

 :) Nice clean carbs also like a nice new in-line gas filter...before you try and fire her up ;)

Back to basics...do you have spark??

With the air box off, do you have gas squirting down the carb throat(s) from the wee right angle copper tube(s) ???

Do you have enough fresh gas in the tank ???

Battery is fully charged ???

                      8).......TIGER..... 8)
                 

[jim328]

Thanks guys, I have synched the carbs by eye as close as I can (looks close). I put a new fuel filter in the fuel line and replaced the fuel line. Definitely fuel getting to carbs.

But there is no gas squirting from right angle tubes but I stripped down the little pump thing on side of carb and cleaned out lines from float chamber and replaced fuel line between carbs. Pulled the right angle tubes out and cleaned and cleaned and replaced the internals.

Tank was filled with fresh gas from empty, Battery is fully charged.

I can't understand why would start ok first time and run up through the revs fine it even idled ok although between 1500 and 3000rpm. It also started an ran that day a couple of times. But now nothing unless I spray engine start down carbs. It definitely seems like a carb issue but I have cleaned them again meticulously with no result.

[Kiwi]

I had a similar problem.  It was my accelerator nozzles.  They where clogged and then not well aimed.  Look at that little right angle tube and see if it shoots gas straight down into the carb, or is it hitting the sides?

[Walt_M.]

I'm going to guess your enrichening circuit(choke) is not working. Either the cable has come off or it is plugged up.

[jim328]

Looks like I will have to strip and clean carbs again. Just out of interest. When the carbs are reinstalled how long should it take to draw fuel through. The float bowls are definitely filling.

[Lucky]

just a few minuets to fill the bowls.

if you haven't already, you need to pull the tank & petcock, remove the petcock, & clean both.  the 'corners' of the tank are lower than the petcock & collect water, rust, etc. they will crap up your newly cleaned carbs.  you should also add an inline fuel filter.

the corners also tend to rust out & develop pinhole leaks. seal them up with your favori2te fuelproof epoxy & coat the inside of the tank with POR-15 or Caswell (NEVER Kreem!)

--Lucky

[sunburnedaz]

I thought the the XZ400 had the same BD-34 carbs as the 82 visions but it didnt have the accelorator pump? Is that correct?

[jim328]

They look like the diagram for 82 carbs minus the fuel pump so I guess they are BD34's. I am pretty sure Roro told me thats what they are.

[sunburnedaz]

That sounds right. Then I guess wikipedia was right. LOL

[jim328]

The problem has been diagnosed. One of my dad's friends is a mechanic with many, many years of experiance. Took him all of two minutes to diagnose the problem as a tight intake valve on the front cylinder. Is there anyway I can do the the job without using the lifter depressing tool or something I can use in its place?

[The Prophet of Doom]

 I'd like to know how he can tell this - engine diagnosis is a mystery to me.

There is a design for a homemade tool made out of a spanner on Lucky's web site
http://www.xz550.com/art_files/ValveShimTool.jpeg

If you are keen you could get one laser cut from the spec.

Although The 400 has totally different valve specs from the 550, the clearances are the same.  If you are looking at shim charts, apparently Haynes is correct, and some of the Yamaha charts are wrong.

Before you crack the engine open, make sure you know where you are going to get gaskets and shims.  Now that Canterbury rides has vanished I don't think there are any Yamaha dealers left in the area.

Let me know when you do this, I'd like to watch

[jim328]

The new Yamaha dealer is Trevor Peirce Motorcycles. They can get the tool for me (there is one sitting around as dead stock somewhere in Australia) but $120.00 is bit steep for me at the moment so I am going to try and make one. If I can't source shims locally Wemoto in the UK have them. I figure the valves probably haven't been looked at for a while so now is as good a time as ever.

As for diagnosis, the mechanic put his hands over both carbs while I hit the starter to create a vacuum and  pull fuel though, when he let go it fired fine on the rear cylinder but flames shot out of the front carb. So he is pretty sure it will be tight inlet valves not closing properly allowing the fuel air mixture to leak past. This should be reasonably easy to confirm with a compression test this weekend.

I am keen to check the valves anyway because  I am really enjoying the sense of acheivement as I complete each project. Just wasn't anticipating the bike providing me with so many. Will let you know once I have the tool made and ready to do the job.