Dell'Orto Carb Question -- Moto Guzzi

Overpaid Slacker · 08-13-2008, 01:51 PM

OK, Pelican gearheads, I'm stumped.

The 'Guzzi runs strong... except one out of every 3 or 4 times I come to a stop (when the bike is warm) it wants to stall. I can feather the throttle and she'll stay alive, but I can't just "hands off" and have her idle. I've adjusted the idle/mixture and I'm pretty sure the accelerator pumps are working as they should. Again, this doesn't happen every time, just often enough to be a huge PITA.

Also, and perhaps related... occasionally when upshifting and rolling on the throttle, she'll want to stall. She doesn't actually die, but the power just goes away. clutch in and blip her, and she comes back, but again it's intermittent.

I suspect these two are related, but do not know enough about these damned things to be sure.

All the fuel lines and filters are new/clean, and I've run a bottle of Sea Foam through her in the past month or so, so there shouldn't be any "gunk" or "old gas" issues.

It's the intermittency that's got me flummoxed. Any ideas?

Thanks in advance.

JP

lendaddy · 08-13-2008, 01:52 PM

Sticky needles(s)?

Tim Hancock · 08-13-2008, 02:07 PM

To take a wild stab at it, I would say the low speed jets (which are very small diameter) are plugged. If the bike used to run good but after setting several months, is acting up at low rpm, it is likely due to the newer gas formulations that have been plugging up alot of bike carbs I have worked on recently. If this is the case, chemical treatments will probably not fix it as the bikes I have worked on each had a couple of these jets plugged solid and even once torn apart, soaking in carb cleaner would not loosen the crap up. I had to carefully dislodge the crap with micro drill bits twisted and inserted by hand.

The new gas formulation is GARBAGE!!!!!

Jeff Higgins · 08-13-2008, 02:52 PM

I've seen the same thing Tim describes. The residue is a very hard, red, almost sand-like in hardness crud that has to be mechanically removed. Nothing I have found dissolves it. Disslodges, yes (as it breaks its chemical bond to the adjacent metal), but that is where your real trouble starts. Now it's free to float around and intermittantly clog things, then settle back to the bottom.

LakeCleElum · 08-13-2008, 03:38 PM

Tim and Jeff are correct. Pull your pilot jets and soak them in carb cleaner over night. Remove your idle mixture screw, spray carbs cleaner in the passages and then use compressed air to get rid of the crap. Check float level upon reassembly.....

bell · bell's Garage

what about a voltage drop just enough for a plug not to fire?

Overpaid Slacker · 08-14-2008, 05:11 AM

Thanks, guys. I'll get on that this weekend. Bell -- the voltage seems OK; which is not to say that a coil might not be hinky, but there's no high-rev missing, so I don't think so.

JP

Tim Hancock · 08-14-2008, 05:54 AM

In case you do not know this already, if you start removing/diassembling carbs, be sure to count and write down the number of turns any airscrews etc are set and do not mix parts from different carbs.

I have no experience with MotoGuzzis or Dellorto carbs, but if you can simply remove the float bowls while still on the bike and unscrew the jets without removing the carbs, this job will be simple. Carbs on many modern bikes can be a b@stard to remove and often need to come out as an assembly rather than remove each carb individually.

id10t · 08-14-2008, 06:02 AM

based on my foggy memory from 356talk, many of the dellorto carbs are very similar to webers... dunno if that will help you any.

Jeff Higgins · 08-14-2008, 06:26 AM

Quote:

Originally Posted by Tim Hancock

In case you do not know this already, if you start removing/diassembling carbs, be sure to count and write down the number of turns any airscrews etc are set and do not mix parts from different carbs.

I have no experience with MotoGuzzis or Dellorto carbs, but if you can simply remove the float bowls while still on the bike and unscrew the jets without removing the carbs, this job will be simple. Carbs on many modern bikes can be a b@stard to remove and often need to come out as an assembly rather than remove each carb individually.

More good advice. While I'm not familiar with Guzzis, it seems to me their longitudenal V-twin might just hang the carbs out where you can do this. This is how I prefer to work on the carbs on my H-D's; their layout makes it very simple to drop the float bowl with the carb still on the bike. All the jets are screwed into the main body, accessible when the float bowl is removed. It will save you some work if you can get to them like this.