Overheating at 25%-50% throttle

[goldeneye]

dan, just relaying information that ive heard mate. it pisses me off just as much as it probly does you to hear of scooters going bang after a dyno run. two of the scooters in question have been well looked after and ran well for the last couple of seasons, one a malossi 210, the other a TS1. as youve admitted, it"s only as good as the operator. so, who tests the tester? is there a benchmark in the industry to reach before an operator is qualified enough to be let loose on such a technical piece of equipment? sean, naming businesses can open a legal can of worms mate, and as they arnt my personal scooters, we"ll leave that up to the owners eh? it was three different dynos though.................

[drunkmunkey6969]

......it pisses me off just as much as it probly does you to hear of scooters going bang after a dyno run......

At least we're in agreement on that then.

[goldeneye]

aye ,yer not wrong dan.

[drunkmunkey6969]

I am wondering if a PHBH just won't do the job and something else would be more appropriate. I'm tired of chasing this problem.

Before giving up, i guess it is at least worth addressing the jets/needles that are in your 'problem' rev range??

So, if 50+% throttle up to 100% full power is OK, you are happy with the peak power that a 28mm delivers, and its just the 25%-50% throttle range that is giving you the heat spike, then we need to look at cooling your engine in that rev range. Without seeing your scooter and going over the whole thing, my initial reaction is that you need to richen up the 1/4-1/2 throttle range to keep things cooler. There are other things to consider, but its an easy and obvious place to start.

Your slide doesnt sound too bad at 40, but a 30 is richer so may be better for your problem? Also, maybe worth looking at the pilot and seeing if you can go larger without bogging down? Lastly, your X4 needle is 2.48, 1.8, 20......so an X13 at 2.50, 1.8, 22 is actually fatter at the working portion you are looking at and has a longer taper...so wont richen up as quick, so this probably wont help. Maybe an X3 at 2.46, 1.6, 22 will get you richer-sooner? Just throwing some suggestions out there to try and help.

So if you can spare the $ to try and richen things up a step at a time, you may find that with a few adjustments (one step at a time) and a few test runs, you get where you want to be? Keep richening up the bottom end until it cures the problem with out bogging.

Lastly the TMX is a great carb, it flows better than the same sized Delly, but its not quite as flexible and adjustable at the bottom end/mid range.....so you may find that you change carb, but dont cure the problem.....or you fall lucky and the Mikuni really suits your engine and therefore teh lack of adjustment is irrelevant for you....but i'd think it would be cheaper to try and work with what you've got and get that right......dont give up just due to frustration and assume a new carb is the answer, as that one will need setting up to!

Hope those suggetsions are food for thought and helps to get you set up, sorry for the 'dyno diversion' and do let us know if you get it cured.

Cheers

Dan

[DaveInPortland]

Thanks for the reply, Dan. The adjustments you mention are all things I have considered. If I had a local shop that stocked Delly parts then I would have gone through all that by now, but since I have to order and wait for the post I have not. I thought I'd get some opinions before embarking on that process.

I have heard a couple of times now that the Rapido really needs to "breathe." As in a larger diameter carb than one might think.

I have worked with jetting both the pilot and the main and know that any larger and it boggs. So, it's down to atomizers and needles, then. I'll just have to order up a handful of each and start mix & matching.

Okay, back to your dyno deliberations! FWIW, dynos aren't all that popular here in the States. There is usually a sportbike shop with one in each major city but that's about it. Scooterists here just don't gravitate toward that style of tuning. After reading the horror stories from you blokes, it's easy to see why. We're much more seat-of-the-pants tuners over here. Sadly, that style of tuning (by me and other "professionals") has brought me three rebuilds in as many years. As such, I'm trying it with my gizmos (EGT, CHT & tach).

I'll post my results once I get it nailed down, even if it means changing carbs.

Cheers.

[drunkmunkey6969]

I have worked with jetting both the pilot and the main and know that any larger and it boggs. So, it's down to atomizers and needles, then. I'll just have to order up a handful of each and start mix & matching.

OK, that's helpful feedback, so try steps 1, 2, 3 below, and to save you $ just try each step at a time until you get the desired effect....

1) Drop the clip on the needle, and just see how that goes first.....its free and worth a try to see how the scooter reacts.
2) Change the atomiser from an AV266 to AV268
3) Try a richer slide (30)

Hopefully by working through these steps you should richen up the throttle range sufficiently to keep it cool without bogging.

[drunkmunkey6969]

I'll post my results once I get it nailed down, even if it means changing carbs.
.

Please do.

Cheers

Dan

[goldeneye]

aye , same here, sorry for jumping in on your thread dave...... hope you get sorted mate. and dan and sean, to show i"m no armchair scooterist, i"ll have a dodge down the shop sometime and you can try and convert me ...... sound ok? no throwing stuff mind!

[sean brady scooters]

and you,ll be very welcome...............

[goldeneye]

cheers sean. much apprieciated.