Repair diaphragm inside the carburetor

[indiandave]

I'm haveing a problem with lossing power on bike at hyw speeds. Have to keep opening thottle to wide open after on the hwy for about 3 miles, is ok before that. It  just slow lose power like the lost of a cylinder.
 
So I pulled the carbs apart and found one of the diaphragm has a cut about 1/4" long thinking it is losing vac.  There where other issue with the carbs that have been corected/cleaned/replaced slow jet with 38's. Also found that the intake o-rings where leaking - the bike was cold harted,  but after you got up to temp idle fine.

So the main question to all, has anyone repaired the diaphragm before? The best price I can find is 69$ shipped to me from SHS powersports. Is there a after market one out there or some where cheaper?

Last question with 38's,  the idle air screw needs to be out how many turns? The bike was Desmoged by PO.
Thanks David

[98valk]

try rubber cement from a craft store or one of the newer silicones. Either way a very, very thin coat.

[custom1]

Sounds like it might be a torn diaphragm in the petcock not allowing the petcock to open fully. The bowls will run dry after a couple miles. If you run at low rpms it will run good forever but as soon as you open it up for a few miles it runs out of gas. Same feeling as a partially clogged fuel filter. If you have a mighty vac, pull a light vacuum on the line that goes to the petcock and see if it hold or leaks down.

[Patrick]

1. The pilots should be set at about 1.5-1.75 turns with 38s.
2. I would think the way to fix the torn carburetor diaphram is to replace it.
3. It sounds like you're having a fuel delivery issue. Its probably time to fix or replace the petcock.

[signart]

Just went thru that same issue, cut diaphragm. This caused a little burble and flat spot for me, but still ran well on open throttle, so may or may not be your issue. Worth a try to repair it, not that big a deal to change.
Also just changed to 38 slows. One & three quarter turns worked great for me. Synced the carbs and I love the way it starts now, no warm up time to speak of.

WARNING: I think the carb sync cost me the loss of chrome on the alt. cover, so remove it before this procedure as precaution.

[indiandave]

Thanks - the shut off valve have been replaced with a Pinge by PO, have checked it all good has in tank screen.  Cleaned and redeye carb kit with all orings and bushing replace. Found some vac leak's. Just need the diaphragm now to test her out. Have set 1 3/4 turns on air idle.

[Rio Wil]

If your pringle is vacuum actuated, you still need to check it for a leaky diaphragm by gently applying a vac and see if it bleeds off, wouldn't be the first pringle that has failed.

One person recently reported a hydrolock and does have a pringle installed....they are not infallible.

[indiandave]

Manual pinge valve(no vac) so that not the problem. Have used rubber cement for tire pacth kit and cut the parts bag from Redeye to fit cut area on both side of diaphragm to test carb work. It does work the cement is still flexable! Not sure for how long, have order parts as I'm looking at a 3000 mile trip in 3 weeks. See you all in Inzane.

[john]

      " try rubber cement from a craft store or one of the newer silicones."           
       very bad advise                                        

[john]

              yes sir ...   
                                   a new diaphragm ...           
                 

[pancho]

That diaphragm operates the high speed circuit in that carb, it is vacuum operated,,, it needs to flex extensively,, Any repair, I would look at as temporary,, like emergency use only..   The new one will clear up some problems as a tear will certainly cause some. 

[Ricky-D]

I don't know if I feel the same.

To me it would be worth a try to fix it.

I mean it wouldn't stop the bike from running so it's not a desperate emergency.

And depending on the location of the damage of the diaphragm and whether it's a tiny hole or a little tear I can see trying a repair.

I could even visualize maybe a small patch with some other material.

The trick would be to use a proper glue (adhesive) that will persevere.

This way you could keep the new one as a replacement.

***

[Len]

You are not stranded yet so repair it with a new one.  If anything throw the repaired part in your bags when you start your trip instead of being worried about it failing, could be a big distraction for 3,000 miles. Just my $.02.

[indiandave]

 I got the new diaphragm today! The repair was to test the carbs as I had gone thru them. Had time off work and wanted to test carbs out before going back to work. I'm working the midnight shift this week for 7 nights in a row.  It's hard to get up and work in the heat of the day then put a full night of work in.
 So the repair has held and is still flexable used rubber cement from the tire patch kit and platic bag to reinforce cut. Only put a short ride on ibike as was I wanted to service the rear end and pulling a new tire on her. On test did not have the problem again with slowly lossing power on the top end after 5 miles on the road at steady pace. Would be at 3500-4000 RPM and fullthottle doing 55MPH.
 What I found on the rebuild on carbs was that all the intake orings where leaking - Flat,(the bike had just started to have a hard cold start issue). The bike was desmoged, pinged  manule s/o and Delmar valve installed by PO(tank valve removed & cleaned screen just a little rust). Found that 3 air valve orings where leaking at orings (fell aparts re oringed everything on carb and new vac lines). Replaced the S/S bushing as one bolt was corroading badly. Had a time removeing 2 of the S/S bushing - used Koll oil but had to peen over the old bushing and light tap out with the old rod/bolt not to damage the threads. Replaced with Redeye bushings. Put new 38's  in for slow jet but the old 35'S where clean, I have a meter pin set for small carb work and check all my jets and passages(also blow all passages). As the problem was mostly on the top end -I did not mess with the sinc screws on rebuild as precheck the butterfly all looked very close. And when pulling the Air needle out I check and all where 2.5 out, I replaced washer and oring 's and put back at 1.75 out on turns. I do not have a sinc gauges, but on my test ride it was very smooth and full of power on the lower end. Also replaced the sinc rubber vac covers as they where cracking badly.
 So on friday 6am I'm off for the weekend and need to install the new rear drive unit back on. As last week I pulled the tire and found the rear drive spline only having a 32nd of the read spline left on it  & the tire flange was about 2/3rds left. The tire had about 5K on it but planing a big trip (about 30 days combind on bike going to Inzane). The Installer over toquerd everything and I'm sure that the tire flange was replace at that time. Unsure if PO knew or not as he bought it from a HD steeler and rode bike only 5k and I'm sure the HD replaced the tire to sell the bike. I know should start a new line on just that Item. Anyway hope to get a ride in sunday to check all the mods out if the rain will hold out. the 15th is coming up fast.

[indiandave]

Well finaly fixxed the Issue with the lose of power at hwy speed. It was a fuel delivery problem. After going thought carbs and replacing a torn diaphragm. The bike still lose power after 2 miles at hwy speed over 75MPR, Note it would take more miles at slower speed's same issue. So after much thought and not wanting to go thru the carbs again (as I was sure that they where rebuilt correct).  I went looking at the petcock and the DelMar shut offs again. I did not install this mod was done by the PO, the 1st thing I see that he pulled pos power off the coil pac. Was unsure if this would afeck the coil or the elec vavle. I was 90% sure that this was a lack of fuel issue. The Manule Pinge valve flowed great, so I removed the DelMar valve and replaced it with a 3/8 fuel line. And off for the road test, Man this worked the bike is runing great and will matain any speed I want.
 This is my 1st time working with a DelMar valve, do these go bad or is it where the power was pulled from the Issue? For the time I'm going just to use the manule s/o valve 1) as my road trip starts Sat 2) I'm tired for pulling the gas tank and 3) all but one of my bike I have to shut off the fuel anyway so I'm always doing it anyway.
Thanks for all the input. David

[BonS]

I presume you're referring to a Dan-Marc solenoid valve that you removed. I've never heard of one failing but I've heard of, and experienced, problems with them because the fuel line was slightly too long which causes the fuel line, when hot, to kink just slightly and starve the engine at highway speeds. I experienced this and cut about 1/4"- 3/8" off the fuel line and the starvation problem is gone.

Regarding attaching the valve to a coil: I had problems at upper rpm's when I tried this. The engine would miss under load at high rpm's such as in full throttle acceleration. Others have not had a problem wiring to the coil, go figure. I rewired and pulled the power from another source and the problem went away.

Glad you got your problems sorted out.

[indiandave]

Yes that the valve name - my bad spelling bad & memory dose not help. The fuel line was not kinked for sure, as was running a inline Fram filter before Dan-Marc valve it was brassed tee right out of valve to short lines to carbs. This filter I added to PO installed item, the problem has been on the bike since I got it ( power Lose). I'm heading out on Sat am to Ia from Fl on bike, so I'm keeping it with just the fuel Line - no filter just the screen in tank around petcock. I cleaned the tank and it seemed to be very clean to most I have come across. Bike ran great to work today no lose of power. Yea! just need to pack.
David

[BonS]

Yup, I agree. I try no to violate my rule of no mods to the bike for at least a week before departure. It's hard to follow that rule, though.

Did you mention the fuel filter previously? Many here have had issues with poor flow through filters that resulted in either fuel starvation at speed and poor flow with low fuel levels. Many have had to go on reserve at about 1/2 tank levels due to filters. Many filters are just too restrictive for a gravity flow fuel system. I don't know which filters have been found to work best, except for the tank filter screen, but a little searching here on the tech forum will find some.

Good luck on your trip, be safe, take pictures and post a trip report when you can!

[indiandave]

I had problem before I added filter. Order all parts from Redeye at once, went with the franken line and filter he supples. I was going thur the carbs after run - 2 can Seafoam, 2 bottles Tecton and 1 can Carb cleaner, it did not clear up ALL the problems with bike but did clear up most(rode bike about 1K in 5 weeks 200 mi the 1st day home). I knew that the bike would be down for a week or two (had other mods to do on bike) - I hate to get a bike apart then be waiting for a part to finsh. After I got the tank off found out what PO had done and that it had been already been desmoged. But the carb's did need to be gone thur. The bowls where fairly clean, but most of the rubber oring/parts where gone or going (here in FL rubber do not last). Before I installed filter the PO had a clean install the fuel line was not kinking.

So I still thinking that the valve is the problem. When I get home from InZane in Aug will reinstall the valve with a switched clean 12v power from battery to see if It still has the problem. As my thinking is that the coil power wire would be a pulse 12v only getting power when the coil is to fire, correct.

[Ricky-D]

There have been numerous problems reported regarding using the dan-mark valve.

The regretful part being that you don't need the valve to begin with.

Self discipline is an easy replacement for the dan-mark.

Holy cow!

***

[BonS]

The coil fires when ground is removed. The 12 volts is continuous. I gave up on the Redeye franken "loop", without his filter, but for a different reason it had to go. I don't know that we've ever done a poll to see how many folks have had good results with it and that would be interesting. I once had the fanken loop, a filter, and a Dan-Marc valve fed by a coil. I ended up with just the Dan-Marc valve fed by the battery when I was done and have been living happily-ever-after. That's not to say that more won't work is isn't better, but for me I finally settled on less-is-more.

[indiandave]

Agreed, Like I said I only had one bike that shut off the fuel by it's self NOW, the St1300.