Homelite Ranger 33cc AIR LEAK?

[banditt007]

I couldn't help myself when I saw a 2 stroke destined for the landfill, so I snatched it up and took it to the bench. Its a Homelite 33cc Ranger Model UT10947D. After checking things over I fired it up (3 or 4 pulls) and it seemed to run normal for the first couple minutes, I didn't have any wood I was just reving it. Then it started running lean for sure like an air leak, RPM went up chain started spinning at idle. Hit the throttle and it bogged lean. It died, pain to start back up even with partial/full choke. Backing out the low speed screw seemed to not have much effect once it started running lean. Before the saw started running lean it was working as expected, carb was reacting normally to adjustment, steady idle, reacted good to throttle ext.

***Update see post #3***

Here is what I checked and checked out good:

-Known good gas
-Piston looks perfect on both intake and exhaust, has factory lathe marks still in it. Ring has spring and is not stuck in the groove.
-Looked at the cylinder from intake and exhaust side and spark plug hole, looks good.
-Compression 150psi cold.
-No carbon blocking of exhaust and piston top looks good
-Fuel tank vent
-All Fuel lines
-Purge bulb
-Fuel filter
-air filter clean and flows well
-No excess build up of wood chips blocking air flow
-Pressed on side of piston to see if it was loose in the cylinder, but seemed tight/normal.
-grabbed flywheel to check for radial/axial play in crank bearings there was zero play.
-bench tested carb but did not open up
-vac and pressure test on engine while slowly turning crank several revolutions did this for a minute or two for both pressure (1opsi) and vac 15 in/hg) zero leak down. Engine was much closer to ambient than warm by the time I did this
-spark plug was tight
-Made sure 4 bolts were tight that hold the bottom clam shell to the cylinder (which are the same bolts that mount the engine to the case)
-There is no intake boot, just the insulation plate between the cylinder and carb, both gaskets were there but gasket between cylinder and plate tore when I removed the plate and seemed soaked with oil and soft. The other gasket between carb and plate stayed intact but seemed age hardened. Nuts that hold the carb/plate/gaskets/intake of cylinder were tight

I made new gaskets for both sides of the insulation plate, and bolted everything back up for testing tomorrow. I hope that it was just the gasket between the cylinder and insulation plate that was leaking when hot, but I'm doubtful!

Has anyone ever had crank seals or base gasket leaks that bench tested good, but failed when hot? Only thing I can think of at this point is something is warping when hot. I'll report back and see if the new carb gaskets fixed it.

PS:
Yes I know this saw is a POS, just a tinkering project not looking to spend any real $ on it!

 

[Jasonrkba]

Had very similar problem on that same saw. I tore it down and cleaned off the carbon on the piston, replaced the oil seals, I believe I replaced the crank bearings, rebuilt carb, fuel lines, primer bulb and it ran like new. I believe it was either the seals or the carb that was the culprit. It had great compression before I started but ran like your description.

 

[banditt007]

UPDATE: Today saw ran great for a minute or so and then started leaning out again, it consistently happens once it gets a little heat into it. New gaskets one either side of carb didn't help. Tried further tightening the 4 bolts that hold the clam shell together when hot-no dice. This time i sprayed some electrical parts cleaner (flammable) around the base gasket/crank seal area and I got an immediate response from the engine. So I tore the whole thing apart planning on just doing the base gasket. The base gasket is just sealant and once I removed the lower clam shell it was obvious that if I used the old bearing cases (rubberized outside) or the shaft seals, I was never going to have a good repair since the rubber had indentations in it and had taken set.

I ordered new bearing cases and shaft seals. The bearings seemed okay, but was thinking of replacing them since I might harm them trying to remove the old rubberized bearing cases from the outter race. This homelite PN are said to be no longer available. The old bearing I can read "ccf 6201 china" I found these NTN 6201 c3 bearings on amazon. Rated to 250F, will these work good? https://www.amazon.com/gp/product/B00P0YHMDO/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1

Any tricks to remove the flywheel and oil gear from the crank without damage?

Thanks!

 

[TBS]

The oil pump just unscrews and the drive gear should just slide off.

 

[banditt007]

oil gear on the crank is definitely a press fit from what i can tell. I think i'm going to have to try to rig up a small bearing splitter and pull it off.

 

[Jasonrkba]

It's been awhile since I had it but I think the gear pulls off and pump just unscrewed. As far as the bearings go, one of those digital vernier calipers is your best friend.

 

[banditt007]

Yup pump unscrews right off from the bottom clam shell, the metal gear that drives the oil pump on the crank is on there good, i'll rig up something this week to yank it off. Crank bearings inner race just slides right on and off the crank no problem there, not like the pro saws where its pressed on. The 6201 bearing i linked to I think is going to be fine, 6201 is a standardized bearing size and the c3 designation allows for sloppier tolerances so it can deal with heat expansion. This thing is such a cheap saw but 2 strokes are fun and its a nice little project saving it from the scrap yard....for now...I'll let you guys know how this thing comes together.

Any word on how these things respond to muffler mod/porting? Exhaust exit looks very small, muffler itself looks fine for flow internally.

 

[TBS]

This one has a ported intake and exhaust.
https://www.arboristsite.com/community/threads/porting-a-33cc-homelite-ranger.258011/

 

[Jasonrkba]

Sounds like you have it under control. Not sure about modding one of these but keep us updated.

 

[NSEric]

I ported its bigger brother the 3816.
It revs 13500 now and cuts at close to 12000 and has lots of power with the small 14 3/8 lp bar. It was only revving about 11000 at max revs before and was gutless.
1/2 of the power gains were from gutting the muffler, it had a very restrictive cat in it, I got rid of that with the Dremel and opened up the louvers with a screw driver.
I widened the intake 1/8 on each side, took 1/8 off the bottom of the pistons intake skirt, widened the bottoms of the transfers, took 1/8 off the top of the piston by the transfers, raised the exhaust port 1/8 and widened it 1/8 on each side.

 

[banditt007]

Just as an update, the new bearings came in, (I went with same spec as the link but from Nachi) like I said I went with the C3 spec. Comparing the new bearings to the old ones, the old ones appear to be standard spec. I say this because the new bearings have notably more play in them. However I'm going to run them, I don't see any harm in the small amount of play they have. Doing research other clam shell engines very similar to this and use the C3 spec also. Should be fine. The above post is pushing me to port it! So might be a bit more time until I get her together.