Zuma 2t fan mod

[jack667]

Hey 2 strokers
I was having some issues with my ‘05 Zuma 2t tuning.
Whenever it ran great, it also ran hot. When I increased the main jet, it would bog down and run slow
So I looked for a new way to cool it down.
I bought a St8 fan from eBay for about $15 including shipping and just put it on tonight.
My temp went from 360+ (maybe 380) to 280F. About 100F lower!
Besides swapping the fan, I also left off the cover.
I had to do so some major dremel work on the fan cover.
Here’s a video of it running:

youtu.be/IQtMqsisdNI

[benji]

360-380 isn't too bad, as long as it doesn't hit 400. 2t motors work better when hot; typically the oem zuma fan works real well even with the cover in place. More air may be counter productive. I'd check your sparkplugs and do some more carb tuning and go back to the oem fan. What jets are you running?

[benji]

If it was running hot because it was lean and you cooled it down with a bigger fan, it will still be running lean. That's not good.

[jack667]

I was running a 95 jet and it was great, but running hot, like 350-360 at WOT, and then I'd pull over to let it settle down. Assuming it would go to 380+ if I kept it up at WOT.

Then I went to a 100 jet and it was boggy and slower. And the temp went down to about 340 max. I ran at WOT for the whole 6 mile test ride.

Rather than swap jets back, I had a modded airbox in the spares box, and I put on the 1/2 that faces the outside of the bike, with a few holes in it and round inserts with foam. Back to running great, but hot again.

Then I did the fan mod and it made that drastic difference on the temp, while full WOT for even a slightly longer ride than usual.

Maybe I'll put the cover back on for a bit of protection.

Here's a photo of the fan and the dremel hack job, plus a few photos of the plug I just pulled. Keep in mind that it's been in a while, through all those test runs mentioned about, plus a few more. I suppose I'll put a new one in but I'm out of BPR8HS and may need to use BP8HS. I've gone through so many of these damn plugs, just changing out for color changes. Huge waste, but also huge pain bc I haven't found a good local source...

[ryan_ott]

Have you tried a 9 heat range plug or checked your gauge or sensor against another one, off the other Zuma. That plug doesn’t really look bad and I can’t see a fan alone dropping temps by 100F. Are you premixing (what ratio) or using the injection pump?

[jack667]

I’m still using the stock pump

Both zumas are on ‘8’ plugs but the black one uses BP8HS, non-resistor bc I put on that nology Hotwire.

Since I need to buy plugs anyway, I could get some 9s. I may have one but I think it’s BR or BP and not BPR. Ugh!

[benji]

Are you running an oem carb? If so, you may do better with an unmodded airbox with just the snorkel removed. Most Zuma guys use a 85-90 main jet (88 seems popular) with the oem box and a bbk and an exhaust. 350-360 isn't bad on temps, if a 95mj jet ran at 350-360 then maybe a 98mj would be better than a 100mj but if your using a foam filter that may be a little lean.

[jack667]

I’m running a dellorto 17.5 carb so slightly larger than stock. Airbox was stock except with a UNI filter so slightly more flow. Malossi reed block with minor Venturi so there’s that.
All that said, 95 was good, so just a bit bigger than ytou suggest. I could have swapped back to the 95 when I found the 100 to be too big, it went with that slight airbox mod instead.

[ryan_ott]

When you get to your 350-360 is that at 100% full throttle or cruising at part throttle 50-85%? Anything less then full open your on the needle and you may need to adjust the height or a thinner taper needle. Part throttle is what really heats up a 2T.

[jack667]

Mostly and almost exclusively WOT. That’s my test run. And that’s mostly how it’s driven unless there’s traffic

[90GTVert]

I've seen more than a 25F drop in CHT from using a 49cc fan to a 90cc fan on the Chinarelli. 100F is a ton. I did record a 70F drop at part throttle once, but that could have been just a slight difference in where it was on the needle from run to run coupled with the fan. I have noticed that some sensors are more sensitive to airflow, so maybe that could be why you see so much of a change? 100F actual CHT difference seems like an awful lot.

At any rate, I would stick with the new fan. If you can clean it up and run a shield of some sort, great. If not, I use a scoop on mine and have it wide open and so far so good (many years and miles).

I've seen them run cooler in the same state of tune and then they have been less prone to seizing and spark knock. Should cool the cylinder itself a little better as well, which hopefully would result in less heat soaking to the intake charge, though I don't know if it would be to a significant degree. Plus, your rings exchange heat with the cylinder walls and the greater the temp difference, the better that works. I'd think cooler cylinders would offer a benefit keeping the piston cooled too. I've never had mine run better from running hotter only. If that were the case, I'd toss my LC kit and all of it's hassle straight in the junk pile and go back to AC. What I've noticed in reality is that the cooler everything stays, the better it consistently runs for me. I'm sure there's a limit to that, but I'd be kinda surprised if most of us could get there with any typical air cooled rig.

[repherence2]

Jack667, I did that fan mod to my chinarelli several years ago. I didn't feel comfortable with the fan exposed like that. I'm a submarine machinery mechanic and exposed rotating machinery is a potential hazard. So I went to the store and bought a round mesh bin. It can be found in the "organization" section of some hardware stores or maybe even Walmart or Target. It's a whole line of bins/trays made of small diamond mesh, they have round bins, drawer organizers, small trash cans, all of them made with the same mesh. I found a cylindrical bin made from the mesh, about 6 inches in diameter (I could be wrong on the diameter), and the flat bottom was mesh too. So I had cut the bottom of the bin off, leaving about 3/4" -1" from the metal reinforcing ring at the bottom of the bin. The bin started out probably about 8" tall, but I cut away the top 7" of the bin, leaving about 1" of sidewall along with the bottom of the bin. I used Shoe Goo to attach an air scoop to the underside of the bin. Then I used Shoe Goo to glue the strainer/scoop assembly to the shroud. My idea with the mesh was to provide protection from rotating machinery, as well as to prevent leaves and other trash from getting sucked in and blown into the cylinder shroud.

this sort of mesh

[jack667]

awesome!
What's cool about my mod is that even though the fan cover looks like (and is) a total hack, it's actually not bad. I spent considerable time making enough room for clearance, while still leaving enough material to secure the original outer cover. I have that on now, but I haven't done a test run yet. If the temp still stays low enough with that cover, I'll leave it. But if not, I can come up with a screen like you did reph, but it should be easier for me if I can just use those three screws and their holes, from the OEM outer cover.
I'll report back after a test run with the current setup.
In the meantime, I ordered another one of those fans for my other Zuma, plus one more for a spare...
Also, since I did remove the plastic screen when I hacked up the cover, I could replace with another screen, and the original outer cover...  That original screen would only prevent large items from getting through.  hmm

[SMALL CC TEK]

Stick a cap full of oil in your fuel . Oil is a coolant also not just a lubricant try it ! lol You did say your using a stock oil pump i think ....

[harleyracer59]

Feb 11, 2019 23:00:02 GMT -5 SMALL CC TEK said:

Stick a cap full of oil in your fuel . Oil is a coolant also not just a lubricant try it ! lol You did say your using a stock oil pump i think ....

the only thing with that is even a little amount of oil like a cap full into our little gas tank volume can take you from running stoich or rich to running on the lean side.  
   any time you add oil to the fuel supply you need to  check mixture and usually upjet because the oil on fuel supply takes away from the amount of fuel the jets are providing.