# 4 cycle Ryobi trimmer



## nbpt100 (Jun 1, 2015)

I was tuning up a Ryobi 4 Cycle trimmer RY34421 and found the timing belt to not align completely on the cam shaft timing pulley. The Belt is about 1/4 wide and only about half of it rides in the cam pulley. It is an apparent alignment issue. The cam pulley is unflanged.

I can't get a good look a the crank shaft pulley with out taking a whole lot apart. From the exploded view diagrams there is no depiction of it.
Was thinking If I could get at it it may be a separate pulley from the shaft and I can align it better with the top cam pulley. If it is made into the crank shaft then I am SOL. 

The top pulley is plastic and pressed on to the steel cam shaft. I gently pried on it to see if it would move and it is on there real good. It may even be heat staked on. It does not appeared to be keyed. if i move it I dont want it to rotate and throw off the timing. Most importantly I don't want to break it and make this machine junk. Neither pulley is called out on the parts list.

It looks like a Royal PITA to take everything apart to get at it. (I need a spanner wrench which I don't currently have to remove the clutch.) If the crank pulley is not adjustable on the shaft then I would have wasted my time. 
Is it a design or a MFG flaw?

Apparently it has likely been running this way (with only half of the belt engaged on the cam shaft pulley) from the start. 
I may have to leave alone.
Any constructive thoughts appreciated.


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## 30yearTech (Sep 14, 2006)

Those engines are built to be replaced and not repaired. Most of them do not even offer much in the way of repair parts.

I think the timing belt on this may run off of a pulley on the flywheel, but I don't get into many of these units, as it's often more expensive to repair then replace.

Best of Luck with it...


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## finaprint (Jan 29, 2006)

Just the shaft bushing or bearing wear can tilt the belt one way if worn enough to tilt the pulley. Is there any tensioner on it? Sometimes BACKING OFF tension can allow a belt to align better, I know it seems backwards but how I align Ford zetec 4 cylinder belts all the time, they have no belt guide flanges on pulleys and belt drift drives people crazy on them. The tension is too tight on belt, the extra friction then allows belt to walk more based on two pulleys not dead perpendicular to each other. That can be due to shaft or the pulley shape itself, I've ground a crown on pulleys before to get the belt running on them to hunt back to the middle. Once the belt has edge ridden enough it pretty much tends to stay that way, the belt fray at the pulley edge then locates the belt on pulley. 

Just some thoughts.


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## nbpt100 (Jun 1, 2015)

30yearTech said:


> Those engines are built to be replaced and not repaired. Most of them do not even offer much in the way of repair parts.
> 
> I think the timing belt on this may run off of a pulley on the flywheel, but I don't get into many of these units, as it's often more expensive to repair then replace.
> 
> Best of Luck with it...


I was expecting at least one answer like this. I am not disagreeing with it but it would be nice if I could just easily make an adjustment and move on. The timing belt pulley is not in view. It does not appear to be part of the fly wheel but I guess I can't rule it out. If it is, then there is no adjustment and it is built this way.

What do you tell the owner in this case? I am into it for a few hours.

The belt has decent tension and it may stay in place. But it makes me a bit uneasy just knowing it is like this.


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## nbpt100 (Jun 1, 2015)

finaprint said:


> Just the shaft bushing or bearing wear can tilt the belt one way if worn enough to tilt the pulley. Is there any tensioner on it? Sometimes BACKING OFF tension can allow a belt to align better, I know it seems backwards but how I align Ford zetec 4 cylinder belts all the time, they have no belt guide flanges on pulleys and belt drift drives people crazy on them. The tension is too tight on belt, the extra friction then allows belt to walk more based on two pulleys not dead perpendicular to each other. That can be due to shaft or the pulley shape itself, I've ground a crown on pulleys before to get the belt running on them to hunt back to the middle. Once the belt has edge ridden enough it pretty much tends to stay that way, the belt fray at the pulley edge then locates the belt on pulley.
> 
> Just some thoughts.


Interesting input and I appreciate it. The belt has what I would judge to be normal tension. Bearings seem to not have any play or wear. But with out taking the clutch and fly wheel off it is hard to say


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## 30yearTech (Sep 14, 2006)

nbpt100 said:


> I was expecting at least one answer like this. I am not disagreeing with it but it would be nice if I could just easily make an adjustment and move on. The timing belt pulley is not in view. It does not appear to be part of the fly wheel but I guess I can't rule it out. If it is, then there is no adjustment and it is built this way.
> 
> What do you tell the owner in this case? I am into it for a few hours.
> 
> The belt has decent tension and it may stay in place. But it makes me a bit uneasy just knowing it is like this.


That's the answer I give, because I have already been through it before. I had a similar one that the pulley on the camshaft broke. I tore it all down, thinking I could replace the cam and it shouldn't be too expensive, but when I tired to get a camshaft I found I could only purchase a short block. The S/B cost more then a replacement trimmer, not including any repair labor. This makes it obvious that the manufacture want's to sell units and not deal with parts. 

Now unless it's a very minor repair, I tell most of my customers that it's probably cheaper to replace then repair.


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## nbpt100 (Jun 1, 2015)

30yearTech said:


> That's the answer I give, because I have already been through it before. I had a similar one that the pulley on the camshaft broke. I tore it all down, thinking I could replace the cam and it shouldn't be too expensive, but when I tired to get a camshaft I found I could only purchase a short block. The S/B cost more then a replacement trimmer, not including any repair labor. This makes it obvious that the manufacture want's to sell units and not deal with parts.
> 
> Now unless it's a very minor repair, I tell most of my customers that it's probably cheaper to replace then repair.


I went in to this thinking a tune up will get this thing running and it still may. I am just very uncomfortable with how that timing belt is tracking.

I will tell the customer what i found and that there is not much practical I can do to solve the issue. I will suggest they run it until it dies and not to put any more into it.

I feel bad because they could have put the cost to tune it up into a newer used or new machine. Plus if this dies in a short while I don't want them to think it is due to negligence on my part.
The machine does not have much time on it from the looks although it is about 5 yrs old. 

The plugs tend to foul on this design if you don't store it top up. If you store it on the side the oil in the sump can leak into the valves, then into the cylinder. Hence a fouling condition.

Not a great design although I like the idea of going with a 4 cycle vs. electric. I know Ryobi is a homeowners brand but I thought they would be better at parts support on something 5 yrs old or newer. But no....... it is a throw away brand. I am sorry to say.

Years ago I owned a Ryobi 12volt cordless drill when they just started to enter the market. I liked it. It served me well. When both batteries stopped to hold a charge I looked to buy new batteries and they were no longer available. It was about 12 yrs old but heck it was working fine. I was stuck with a decent drill but could not use it because the unique battery it used was not available. That is sorta what this feels like. Obsolescence is quickly designed in by the Manufacturer. You are better off and paying more for a Stihl or Husqvarna. That is what I will be telling folks.


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## nbpt100 (Jun 1, 2015)

As it turns out I was able to slide the cam shaft over a bit by hitting it a hammer. The belt tracks right on the pulley now when I turn it by hand.

It is pressed in to bearings. I hope it will not migrate back to where it was but for now it looks good.

Just an FYI the crank pulley is not part of the flywheel. To access it you have to remove the crank shaft. And even then from what I could see there was not space to move it either direction.

My take away is pretty much what 30 Year said and that is pass on these types of machine unless it is very simple and pretty much a sure thing.


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