OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Trimmers and Brushcutters Ryobi Trimmers & Brushcutters Ryobi scrub hornet Mark2

Hello Chaps, I was out door king around the suburb on the weekend and picked up a Ryobi scrub hornet mark2 from a kerbside [gutter] pickup. This machine is an oldie but a goldie. The only problem I could see was the primer bulb is non existent and the fuel lines are loose in the holes in the bottom of the fuel tank, so I assume the fuel lines are supposed to seal in the tank after they're pushed on the tails. Also the cutter guard is missing and I reckon another Ryobi model guard will fit but I have no idea...can anyone shed a little light on this? Cheers

Hi wassie, welcome to Outdoorking.

I am under the impression that all Ryobi Hornets have the usual Ryobi half-crank engine. To me, all half crank engines are garbage, and Ryobi ones at least as much so as others. I would not pick one up out of the gutter if it were in perfect working condition. There are plenty of good full-crank line trimmers available for very little money second-hand, so I do not understand your interest in a half-crank one. (I recently bought a nearly new 25 cc full crank one on ebay for $1, fixed it in 90 minutes without replacing anything, and it works better than any trimmer I've used up to now. Aldi used to sell them for $70 new.) However that is your business of course.

Where fuel lines pass through the outside of fuel tanks, they have imitation rubber or plastic grommets to seal against fuel leakage. The grommets are available as generic parts, on ebay or from a dealer. Just measure the size of the hole in the tank to ensure you get the correct grommet. The priming bulbs are also readily available - there seem to be 2 standard sizes, with the 19 mm size fitting the small machines such as yours, but measure the mounting to be sure before you buy one, or just buy one that is sold for the small Ryobi machines. Generic cutter guards are available for bent shaft machines, but they cost far more than a decent second-hand machine, so it seems more practical to get one from a tip shop for about $5 with a line trimmer thrown in for nothing.

Thanks GRUMPY for your reply, and your thoughts on half crank engines. The line trimmer I'm talking about has 34mm bore and about 30mm stroke, straight shaft and the dreaded half crank. It'll have to do cause it's the only one I own. Which grommets do you recommend for the fuel lines, is imitation rubber impervious to petrol? With the guard I might have to make one out of polycarb. Cheers Wassie

I think the trick is to read the product descriptions, and see if anyone on Outdoorking or elsewhere has experience with them wassie. The only replacement fuel line and grommet I have personally used was bought from a mower shop, and I have no idea where the shop bought it from. However it seems likely that the shop obtained it from one of the Chinese sources used by a multitude of ebay sellers, since nobody suggested it was a genuine part. Incidentally I only kept that chainsaw for a couple of years, but the grommet was an excellent fit and completely leak free.

The artificial rubber products used for grommets are generally resistant to fuel, and should last for a number of years. What that number is, of course, can only be determined by trial and error. I'm currently playing with a 30 year old Echo SRM200 DA trimmer/brushcutter which still has its original grommet, and it looks good but may have grown slightly since its flanges, while admirably flat, are not really tight on the tank top at this stage. The fuel hose is also original, and the submerged parts of it have grown somewhat, though it still seems to hold the submerged filter successfully. However I am not going to assert that randomly selected Chinese suppliers are using the same synthetic rubber as Echo used long ago. There is a good chance that the available materials have improved, of course, and there may now be cheap materials that outperform ancient premium materials.

hi could you explain what is half/full crank please.

A crankshaft normally has a main bearing on each side of the crankpin, so the loads imposed by the piston are absorbed evenly on both sides. This makes the crankshaft what in structural analysis is called "simply supported", and is the most efficient shape: it achieves the required strength with the minimum weight of metal. That is called a full crank.

A half crank has only one main bearing, with the crankpin out to one side of it: it is a full crank cut in half at the crankpin. This is what in structural analysis is called "cantilevered", and unless you increase the size of the main bearing substantially, it gives much less strength, more deflection, and more vibration. Actually even when you do increase the size of the main bearing as much as is practical, it still gives all of those things. In structures, it is sometimes done because there is no alternative. In engines, it is only done because it is cheaper.

thanks for that now it makes sense.

[quote=grumpy]I think the trick is to read the product descriptions, and see if anyone on Outdoorking or elsewhere has experience with them wassie. The only replacement fuel line and grommet I have personally used was bought from a mower shop, and I have no idea where the shop bought it from. However it seems likely that the shop obtained it from one of the Chinese sources used by a multitude of ebay sellers, since nobody suggested it was a genuine part. Incidentally I only kept that chainsaw for a couple of years, but the grommet was an excellent fit and completely leak free. The artificial rubber products used for grommets are generally resistant to fuel, and should last for a number of years. What that number is, of course, can only be determined by trial and error. I'm currently playing with a 30 year old Echo SRM200 DA trimmer/brushcutter which still has its original grommet, and it looks good but may have grown slightly since its flanges, while admirably flat, are not really tight on the tank top at this stage. The fuel hose is also original, and the submerged parts of it have grown somewhat, though it still seems to hold the submerged filter successfully. However I am not going to assert that randomly selected Chinese suppliers are using the same synthetic rubber as Echo used long ago. There is a good chance that the available materials have improved, of course, and there may now be cheap materials that outperform ancient premium materials. [/quote] G'day grumpy, I did look on ya site for scrub hornet mk 11 but got zilch. I got fuel line and primer bulb off ebay, built a guard outa ali minuim and watta know she fired rite up, runnin sweet as a nut. And must add the half crank motor don't vibrate much at all, the maufactura must balance them or sumthin. Cheers wassie