404cc Yanmar/Clones - Throttle Idle / Springs: Consolidation

[snoopy]

I am going to get as many owners of these engines to answer the big question which nobody (so far) has answered.

The throttle mechanism on this engine works by force. Two springs increase the force around the pivot, one tries to make the engine stop, the other increases fuel payload.

To make the engine idle the springs must be strong otherwise it will not go back to idle easily or it will idle for a bit and then die. The dilemma comes when operating the bike in the real world over some distance. The pull against the springs will cause considerable wrist pain.

I have tried reducing spring strength. I've made a rod that comes up from the pivot and increases moment.

Right now I run only the return spring. This makes the throttle useable on a daily basis but I have no idle which is really annoying.

What solutions do people have/use/advise?

Andrew

[henneberg]

Hi,

I have uploaded a small video: http://youtu.be/E3ZOPgWJOSk with my Yanmar throttle mods.

at the place of my finger there will be an idle adjustment top-down screw

rdgs, Erik

[snoopy]

Have you tested to see if it works yet? Typically the throttle will be too much for the wrist on longer journeys.

Andrew

[henneberg]

Hi,

Yes it works OK, the handle wrist can be shortend by modifying to the top lever to have the throttle cable run closer to lever center.

rdgs, Erik

[snoopy]

How well does it idle?

From what I can tell the only way to get a good idle is to have strong springs to keep the governor in check. The force required in the springs is what makes the throttle hard to use at the user control.

[XLerate]

For cruising you could fab up something like at the link, a throttle lock. Some are a clamp that grips twistgrip throttle spindle at any speed desired, sort of like a pincers or pliers:

http://images.search.yahoo.com/search/i ... se+control

The simple 'Throttle Rocker' lets you use palm of hand for leverage on twist grip.

[snoopy]

I used one of these when I took the bike to Barcelona from the UK. It was still immensely painful.

The trade off is no idle. I'm wanting to find anybody that has solved both problems, but it doesn't seem possible.

At the moment I'm thinking of a second choke type cable/control that pulls and fixes it in idle. Same ideal as a throttle lock.

[snoopy]

I've attached my solution so far. You can see a large rod which has been welded to the original pivot point. I've done this to allow for tweaking without having to remove the engine.

The left spring has a good feel to it. On the right I'm not running a spring however I'm testing different springs to try and get the idle sorted. No joy so far.

Andy

[XLerate]

I can't begin to figure out how all this is supposed to work from the picture.

I'm most familiar with Bosch injection pumps. I would expect a lever mounted on a shaft that rotates & makes fuel adjustments inside pump, either moving a piston or valve etc. On the Bosch the throttle lever section is all spring loaded & even with no linkage attached the engine returns to idle.

From the picture I can't see what is supposed to move or where it moves, or how, or what anything does mechanically. Is there any source for mechanical info on the design you're dealing with?

[snoopy]

There is a pivot point like the Bosch, this controls fuel payload. There is a governing wheel so as the engine struggles the force required to maintain the same fuel load increases. The engine will not idle without the correct spring force in either direction.

[snoopy]

I wonder if its just mine, I'm unable to make it idle for more than a few seconds; it'll either rev up and die.

Perhaps having the springs at the top of the lever rather than near the pivot gives too much scope for moment at the pivot . I've tried various strengh springs but to no avail.

Andrew

[Nanko]

The idle position has to be fixed with an adjustable screw.
I understand you are using two springs to keep the throttle lever in the idle position
But the force on the lever varies with RPM due to the governor action, so there never will be a balance between governor springs and (external) idle spring
At spheres IB40 we modified the twistgrip,a strong spring keeps the position in idle.
Now the idle speed can be adjusted with the cable length.
Forcing the twistgrip in reversed direction presses the extra spring,and the engine stops.

[snoopy]

The idle can not be fixed. If you do this then when the engine is under less load than idle (such as going downhill with no throttle) the engine will speed up.

I'm also gathering posts from other places and putting them here. Here's another guy from Germany that no longer can idle...

---------

Hi Andrew,,

this is the same with my engine, the idle is set up in such a way that I have to pull throttle from time to time, else the engine dies.

I have become used to this, and its cool as I don't have to do anything to stop the engine after a ride.

There was a time, when I had very good idle, and this was when I was having and old used injection pump installed in my engine.

However I had the feeling that this old pump was also leaking, it was leaking diesel into the engine oil. I then replaced it with a brand new pump, and the good idle was gone too ... there must be a relationship ...

Charles

[Nanko]

It looks like you are using the stoplever to control engine rpm.
No possibility to change the spring tension on the governor?

[XLerate]

The idle position has to be fixed with an adjustable screw.

I understand you are using two springs to keep the throttle lever in the idle position. But the force on the lever varies with RPM due to the governor action, so there never will be a balance between governor springs and (external) idle spring.

Yes, this is what I have difficulty understanding. In 50 years of wrenching I've never seen any engine that didn't have an idle stop adjustment or idle stop screw, whether it was governed for speed or not.

Using 2 opposing springs to supposedly balance moving parts at a central point of idle isn't common to any engine I've ever seen, even generator sets.

"The idle can not be fixed. If you do this then when the engine is under less load than idle (such as going downhill with no throttle) the engine will speed up."

But there is no such thing as less load than idle. Idle speed is the zero point of useable rpms regarding the throttle. Even under deceleration the engine should not drop below idle speed for over-the-road use.

"There is a pivot point like the Bosch, this controls fuel payload. There is a governing wheel so as the engine struggles the force required to maintain the same fuel load increases. The engine will not idle without the correct spring force in either direction.
There is a pivot point like the Bosch, this controls fuel payload. There is a governing wheel so as the engine struggles the force required to maintain the same fuel load increases. The engine will not idle without the correct spring force in either direction."

Yes, some governors may add fuel when engine load increases, but only on stationary engines like generators which must maintain a constant voltage output. Vehicle engines can't function this way because every time you come to a hill with more load on engine it will try to increase speed. Without the generator being attached to engine there is no effective stopping point or balance point for governor in either direction of rpm's. That is, there's no reference point such as voltage output from a generator.

Diesels for road use only have a governor for maximum rpm's, only to protect engine from over-runing. That is all that's needed or desired. It sounds like you need to split the functions up on your throttle & governor linkage. Install a setscrew throttle stop of some kind, then disconnect the throttle from the governor, where the spring automatically compensates for more load on engine to cause engine to speed up. Keep the linkage or change it so that governor only regulates maximum rpm's, nothing else.

You may have to change the entire throttle linkage from the throttle shaft on out but it sounds like it's physically impossible to make the current setup work correctly. Possibly you could find a similar engine that's designed for another use, instead of a constant output generator set, and adapt the normal variable-speed throttle parts.

[snoopy]

This topic is important as so many are putting the 10hp clone into bikes. I'm glad its getting some response.

The engine does not support a fixed idle screw because when in drive downhill it is easier for the engine to turn over than if it is sat with no load on it. Essentially this causes some attempt to accelerate when going down hill.

Yup the engine is designed for fixed speed operation.

We need some pictures of _anyone_ that has a) managed an idling engine without needing to touch the throttle at all over several minutes and b) a setup that does not use such high tension springs that the throttle control is uncomfortable on the wrist.

It seems mine and Charles engine have the problem that having something close to idle still needs throttle 'pumps' to stop it from dying.

[snoopy]

But there is no such thing as less load than idle. Idle speed is the zero point of useable rpms regarding the throttle. Even under deceleration the engine should not drop below idle speed for over-the-road use.

The throttle does not set RPM it sets fuel payload. Less fuel is needed going downhill in drive than with no load at all, hence the engine will try to accelerate. Yes not much but certainly by a noticeable amount (and it's dangerous with crappy Enfield brakes).

[Nanko]

The only way to keep a diesel engine idling is adjusting the governor spring.
As we found out when we did a "clever" mod on spheres IB40
The governor was bypassed and the throttlegrip operated the fuelpump directly
The engine was idling for few seconds and died..or ran high in rpm

[skoleskibe]

I don't see the problem, i've been using a twin cable setup for my yanmar for quite some time now, and it works flawless.
One cable to the twistgrip, and one cable to a chuke leaver.
Once startet, i set the idle speed on the choke leaver, and then forget about it, until i need shutting the engine off, which is done by setting the idle too low on the choke leaver.
regarding spring tension as felt on the twistgrip, i dont have any problems, the spring tension is all what you'll have to overcome.

Have a look !

http://www.youtube.com/watch?v=GhGXD-uk ... gnnGsg1qXV

[XLerate]

If it was me I would study the system and determine what mechanism movement adds fuel to engine. There should be a rotating shaft coming out of injection pump, or else a lever on a shaft.

If there's a shaft, attach a flat plate bellcrank on end, preferably welded in place. Drill holes in bellcrank for pull cable throttle cable attachment and adjustment for different lengths. Use additional hole for throttle return spring, to return engine to idle stop position when not fueling or accelerating.

Fabricate a bellcrank stop, with screw adjustment that's firmly attached to engine, so that bellcrank can only rotate freely in fueling direction but is stopped from rotating in defueling position by an adjustable screw, which sets idle speed.

If there's already a lever instead of a shaft requiring a bellcrank, then simply fabricate an adjustable idle stop for lever, to set idle speed, with return spring for idle position. The throttle linkage mechanism on other small engines like mower, roto-tiller, garden tractor, chainsaw etc. may be copied for your diesel, it's very simple in design.

Diesels offers very little compression braking when defueled. There's no need to ever lower engine speed below normal idle speed. Doing so stresses the engine, trying to recover rpm's from below designed idle speed to fueling and acceleration speeds.

With a proper idle stop and return spring no other spring is needed for the twist grip throttle linkage. This simple fabrication will solve all the problems and be much, much safer and easier to use.

[snoopy]

I've fabricated another section to my throttle setup which will allow for a fixed minimum fuel load not based on tension, I'll see how it goes and will report back.

[XLerate]

Sounds good, I hope it works much better. That's one of the main problems when adapting a stationary type engine for vehicle use, especially an engine originally set up for a generator. Hopefully you'll end up with full control of throttle.

Some of the diesels used on welder sets have an extremely complicated throttle mechanism to maintain Constant Current or Constant Voltage output, or in the worst case, both Constant Current AND Constant Voltage output! Fortunately yours is a much simpler system in the first place.

[old clunker]

This is what I've got on my motorbike diesel engine set up. Hope you can make some sense of the attached pictures, it's just that it all happens in a very confined space between the engine and the pre-unit gearbox. Works very well, and just feels like normal motorbike throttle control.
The engine speed adjustment plate is mounted onto the front face of the gearbox.
The fuel cut off solenoid can either be bought from Pricepart Motorcycles, or Direct Equipment sales - diesel generator parts. Whichever is the cheapest at the moment.
Also see Dougy's Harley Davidson build first page. He has a clever solution, using a spare aluminium bicycle brake arm to use as the throttle set up.

[henneberg]

Thanx for the pictures with explaining embedded text.

My solution is very similar to yours, but I have omitted the fuel cut off solenoid because it consumes approx. 3 amps at fuel flow ON, and I want to be able to start without relying on the battery state

The decompressor handle is used in connection with a cable and a small lever to pull back at the fuel lever where the acceleration adjustment takes place

Currently I am going to move the battery down behind the gearbox. A YTZ7S battery fits nice in there

rgds, Erik

[coachgeo]

Thanx for the pictures with explaining embedded text.

My solution is very similar to yours, but I have ....

If there is no pictures "it ain't happend"

[henneberg]

hi,

here is a close up of my Yanmar fuel cut off set-up:

The battery mounting behind the gearbox is to be "picturized" later on in:

https://www.dieselbikeforum.com/view ... 991#p11991

rgds, Erik

[snoopy]

Several people have now commented that the fuel pump is the issue with several unable to provide the necessary pressure at low RPM. There are lots of manufacturers over at alibaba so it's pot luck unless one buys a Yanmar.

Charles, 'salad oil' website says his used to idle then he replaced due to a fuel leak and the new one is unable to keep up.

[skoleskibe]

buy spares from a european dealership, such as Rotek i Austria, then you are covered if the pump doesnt work properly

[skoleskibe]

I used one of these when I took the bike to Barcelona from the UK. It was still immensely painful.

The trade off is no idle. I'm wanting to find anybody that has solved both problems, but it doesn't seem possible.

At the moment I'm thinking of a second choke type cable/control that pulls and fixes it in idle. Same ideal as a throttle lock.

well thats essentially what ive done. However mind dont seem to demand that much power of the wrist as you describe. I've mounted mine at the outmost possible hole in the govenor, bypassing the rev setting arm, but connecting the cable through the spring.
regards