Newbie needs help

[Russwel28]

Hi, I'm new to this site as well as four strokes, so I would appreciate help with my latest project, which is a fzr400 3jt, which I'm doing up. I bought the bike this week, and even so it's far from mint, it is complete, I knew the bike had low speed running problems, cutting out etc when I bought it and was told that it was down to the carb rubbers from carb to engine having splits in them, so the first thing I done was to remove the carbs to inspect them, and sure enough they were badly split on the outside, but the inside of them seemed to be fine, so I'm now starting to doubt that the poor running issues and low speeds is down to this, so I'm after any suggestions as to what else it may be.
Also four strokes are a bit alien to me as I have always had two stroke. I took the carb bowls of to inspect and would like some help with them also, I notice they seem to have what look like two main jets as well as a pilot jet, is this correct and why, also would like help with valves as I have never had to set any before, how to do it, settings etc. basically I need help with a lot or will do over the next few months.
Oh forgot to say, she starts up fine and seems to idle well, but is a bit sluggish when you rev her at idle, she will rev to about 4-5000 then seems to hit a wall, but as she gets a bit warmer she will start to rev past this, but seems to be stuggling, I was told by the last owner that she has no problems at high speed. She has a aftermarket exhaust, so no exup valve.
Any help appreciated.

[DonTZ125]

Rather than two main jets, you have one main and one starter / enrichener jet. They are physically interchangeable, but one flows roughly twice as much fuel as the other - pay attention when doing carb work!

Air leaks in the boots aren't always visible on the bench. With everything assembled and the engine idling, spray some wd40 around the boots - if the engine speeds up, you have a leak. Once that's sorted out, the carbs probably need a good strip, clean, and sync.

[Evilchicken0]

First thing would be to clean the carbs. I don't think it will. Cure the problem but it won't do any harm either.
I'd say the system has changed the fueling so the carbs really need setting up for it.
If the valves were badly out I'd expect it to be hard to start too but again it would be good to check them to make sure.

There isn't a manual for this bike but the fzr 600 r foxeye or the thundercat engine is similar you can use that. Have a read through the section and see what you think. Its quite straightforward maybe if your near to another member they can help you out.

[Russwel28]

Thanks for the help, do you know the clearances for the valves etc.

[Russwel28]

Also does anyone know the size of the standard jet set up as they have worn off. And with the new system what should I be looking to change and to what?
Any help appreciated.

[SouthendChris]

I think your problem here is the aftermarket exhaust with no exup valve.

I have virtually finished a 3TJ rebuild and I changed the exhaust for a Swona tapered header item from a race bike (the originals are like the proverbial rocking horse...... ).

It absolulutely refused to start and idle properly. Now I had the engine running perfectly before I stripped it down (you have to be sure don't you!) so i began to question if it was a duff new plug, was it one of R1 coils I fitted or had i not connected something properly????? In the end i gave up and fitted the carbs from the race bike and it runs sweet now. the standard carbs in my view will struggle with a good header and an open pipe

You could try raising the needles one notch but this wont afect the idle as thats what the other jet is for.

Chris

[Evilchicken0]

Yes to be honest I wouldn't mess about with the carbs to much other than making sure they're clean - then book it in for a dyno tune, its not cheap but it will sort the fueling out.

[Russwel28]

I have been in touch with the last owner and he says the low speed problems started when the exup exhaust was on.

[Evilchicken0]

I'd still look to clean the carbs but if that was the problem then you're into the valves.

Checking the valves then, you have a choice - engine in is cramped, engine out will give a lot more access and you'll be able to clean everything up so I'd go that way.
Tank / airbox / carbs off
So - drop the coolant by undoing the bottom hose, take the radiator off.
Take off the pipes
Remove the electrics (most of the connectors are colour coded) and the HT leads.
Take the sproket cover off and take the chain away.
Drop the engine. - It's best to try and drop it onto one of those plaform trolleys (£25 of the bay) makes it easier to move and work on.



Take the gerator cover and the cam cover off - set the engine to TDC on No1 cyclinder (the flywheel mark lines with the crank casing joint at the front) Now look at the cam lobes you'll see the ones that aren't touching the valve guides are pointing 12, 3 or 9 oclock check these tollerances with a feeler gauge. Draw out a diagram and write down the your results. Rotate the engine so No4 is at TDC (the cam lobes will be pionting at each other) and agian measure and write down the tollerances.

That should keep you quiet for a day or so

[HybridSport600]

SouthendChris,
is right on with this one, low back pressure on a carburated system will need to be re-tuned from start to finish. the exup valve controls the exaust
noise...(cali emisions bikes )....and helps to aid in the production of low to mid end power. Completly removing this will require a full carb tunning and sync.
on the newer fuel injected bikes the computer controls this valve and if it is removed it will compensate for this change, carbs do not.....I would also check for weak spark output on the coils if they are original.

[Evilchicken0]

The Cali bike is a 3en2, the '89 model and has quite a lot of revisions the earlier bikes the US got.

[Russwel28]

Hi guys, been away for a few days, but where I'm up to at the moment, is that I have carbs off, giving them a good clean, waiting for new plugs, oil, filters etc to arrive, I have discovered the cooling system has a slight leak from the metal pipe connected to the rear of the cylinders, bought new seals to solve this. I also found the cooling system has a lot of crap in it, also found that one of the plugs was a bit loose.
So here what I'm going to do over the next few weeks, a good service, fix the leak, check valve clearances, put carbs back on and sync. And see how she runs.
But have a few questions, I agree that any change of exhaust from standard, will need the carbs adjusting to suit, this is something I am used to from my tzr's, but the last owner said the low down problems started with the original exhaust fitted, so could any of the other stuff I have found so far influence the running problems.
Also I'm after the clearances for the valves etc, there is a link on this site for the manual for the sp version, can I use the same settings for the valves, plug gaps, carb settings etc.

[Evilchicken0]

Sounds lime your plan is a goer.
How loose was the spark plug ? Maybe when everything warms up this closes and you get compression. The cooling system probably isn't doing you any favors either.
So I recon clean the carbs, sort the cooling system and do the service. Then see if the engine runs any better and then do the valve tolerances, that way you'll find the problem or problems. Using the SP info is fine.

[HybridSport600]

That plug will deff- make a difference in it running smooth, Never hurts to put new plugs in all cylinders, and use a good aluminum anti-seize on the threads.
Here is a fool proof method for eficient cleaning of them hard to get to areas of the carbs that most seem to miss. Buy some plumbers muratic acid and 2 big plastic buckets, mix the acid with water and use a minium of a 60-40 ratio (Acid-water) and fill the other bucket with only water all the way to the top. remove all gaskets, screws and parts from the carb bases. You can do this with them all attached, or seperate. dip them for a maximum of 3 minutes per dip, and after you remove it from the acid mix, dip it straight into the water bucket to stop the cleaning process everytime you dip them.
!!-Beware not to dip them too long or too many times as this will eventually eat the aluminum-!!

When you dip them it will take a second to start, but when it does the mix will start to bubble alot and you will see the solution turn a little cloudy
!!-only in a well ventelated area, and do not breathe the fumes that bubble up it can/will be fatal-!!

once you perform this a few times, use air blow gun and blow out all the holes you find and all over the carbs to air dry them. then clean and re-assemble all the internals and parts. If mixed right it will not harm the rubber or plastic parts. Adjust all aspects such as fly openings,floats etc...re mount and then do a full sync, and they will perform like new as long as the internals are in good shape. We use this method on all our customers carbs and have had great sucess with no complaints or comebacks. any question just ask...

[willandrip]

That plug will deff- make a difference in it running smooth, Never hurts to put new plugs in all cylinders, and use a good aluminum anti-seize on the threads.
Here is a fool proof method for eficient cleaning of them hard to get to areas of the carbs that most seem to miss. Buy some plumbers muratic acid and 2 big plastic buckets, mix the acid with water and use a minium of a 60-40 ratio (Acid-water) and fill the other bucket with only water all the way to the top. remove all gaskets, screws and parts from the carb bases. You can do this with them all attached, or seperate. dip them for a maximum of 3 minutes per dip, and after you remove it from the acid mix, dip it straight into the water bucket to stop the cleaning process everytime you dip them.
!!-Beware not to dip them too long or too many times as this will eventually eat the aluminum-!!

When you dip them it will take a second to start, but when it does the mix will start to bubble alot and you will see the solution turn a little cloudy
!!-only in a well ventelated area, and do not breathe the fumes that bubble up it can/will be fatal-!!

once you perform this a few times, use air blow gun and blow out all the holes you find and all over the carbs to air dry them. then clean and re-assemble all the internals and parts. If mixed right it will not harm the rubber or plastic parts. Adjust all aspects such as fly openings,floats etc...re mount and then do a full sync, and they will perform like new as long as the internals are in good shape. We use this method on all our customers carbs and have had great sucess with no complaints or comebacks. any question just ask...

Top tip=well done that man!

Mods;This should be a quicky sticky.

This mix also makes a spiffing alloy engine cleaner for unpainted blocks/heads/c.cases when sprayed on with a cheap hand dispenser.
Start at the bottom and work up (trust me this stops run stains if left on too long) and have a hose handy.Apply for a short period ,rinse and repeat if neccessary.It will not work on oily parts so thorough degrease is vital.