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Discussion Starter · #1 ·
Hey guys I am trying to get this new motor going. Its a 71 650 bottom with a Morgo 750 top ,bonne head with amal 932's jetted for bonneville and i have those finned carb spacers in between the carbs and mani's that add about 2" in length to the mani. . . 200 mains i think. Everything is new and tight and it fires right up but I if i give it throttle it dies pretty quick. I went through all the neddle settings didnt get much difference in the top 3 , tried the air screw all through in and out , it runs with like half a turn or even with the the screww seated closed. thats where it runs the best. Did the valve lash a couple times and opened them up a tad to give it more room. Didnt check the compression didnt think i had to the way it fires and the rings are not seated its never been run yet. Its a Hartz bros. engine so i have no doubts things are in place. I am wondering if these carbs are too big or the manifolds add a difference to the whole thing or what. timing is set to 38* and I didnt strobe yet. I have another set of 930's but i didnt want to ditch these carbs just yet. Any input will be appreciated. Thanks Loffer. Theres a pic in my avatar, lol.

Oh, its has a mag too i have set these from scratch many times now and havnt had a problem getting a stock motor to run like a top the last few times.
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...if you screw in and the motor do not die...well, you have an air leak or some internal obstructed.

-relating those spacers, I prefer to go with what the factory tested in all those years, because there s a relation between how long are the spacers and the other variables
A relation that seems nobody know exactly what.
 

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Discussion Starter · #4 ·
yep, i have ngk es8 plugs already. im thinking air leak too. I want the spacers to work I can seal them better for sure I could just throw the carbs without spacers or 930's on there but what fun is that? So i have more volumn in the manifold would you think jetting is need to be larger ? It flat out dies with throttle opened. Now Amal air mixture screws enrichen as they go in to seated? Thats what I have read here repeatedly. Most other carbs get richer as the screw goes out. Why would it run with the screw all the way in if the carb was too big? just trying to eliminate some confusion. I guess the next step would be to run the 932 by itself? Possibilty the valve clearance is too tight for new engine? I loosened them up a .001 or so..
 

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yep the further in the jet screw the richer the mixture, did you replace the needle jets or just clean them? and are you sure the 2 little cross drilled holes are open on the needle jet? is it a 106 jet? and how much slop does the slide have in it compaired to the bore? can you wiggle the slide around at 1/2 throttle? if so then that is why it's running so lean, often time people richen up the idle mixture to compensate for worn slides.

Take a can of WD40 or carb cleaner and spray it around the manifolds, it will rev up if it has a intake leak.
 

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Discussion Starter · #6 ·
yep the further in the jet screw the richer the mixture, did you replace the needle jets or just clean them? and are you sure the 2 little cross drilled holes are open on the needle jet? is it a 106 jet? and how much slop does the slide have in it compaired to the bore? can you wiggle the slide around at 1/2 throttle? if so then that is why it's running so lean, often time people richen up the idle mixture to compensate for worn slides.

Take a can of WD40 or carb cleaner and spray it around the manifolds, it will rev up if it has a intake leak.
brand new carbs Tony. 106needle. no.3 slide.. I took off the bowl ,blew them out and shot some carb cleaner up in the main and blew some air in them when i first got them but didnt disasemble the main or needle. I dont think its an air leak cause they are both running very closely in the setting and the way the plugs look and both would have to have the same leak. I will inspect and clean them again and look for leaks . I have did more research and found one person that said they used the spacers with no problems and they had no special needs, so i might be chasing a ghost and ignoring the basics...
 

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Sounds like the pilot jets are clogged. Clean them with a #78 drill bit. Also I see you had the bowls off,if the gasket between the bowl and body doesn't seal, the idle mixture screw acts like yours. Also check your float level. You should also be aware that even new carbs have been found to have junk in the passages. Jack
 

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+1 on the pilot circuits. You might even want to drill out the blanking plug covering the pilot jets visually check the whole thing out and then tap it for a plug or press in a plug to seal it back up. Drilling the pilot jets slightly larger than stock is also a good idea (helps prevent blocking).

Doubt that the manifolds are a problem (longer manifolds will give you more low-end punch), but you should surface both sides of each manifold and the carb manifolds on a piece of glass or surface plate with wet/dry paper. While you're at it, do the same to the float bowls and check the float levels. And of course, good O-rings on the carb manifolds, with locknuts on the studs so you don't over tighten the carbs and warp them.

Whatever the cause, it sounds lean. To test this theory, put some air cleaners on it and see if the added intake resistance (which will make it run richer) makes any difference. If you don't have air cleaners, put some holes in a rag and firmly clamp the rag over the carb intakes to simulate air cleaners. Be careful with this one, though, as you don't want any rag to get sucked into the motor.
 

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I am running two different 750s with those spacers. Ones got two 930s, other has two 932s.
Both motors want small jets. Both are running 180 main jet. Hard to tell from your post but i am assuming you are running twin carb?

The spacers are a bitch to seal! Thin coat of ultra black silicone does the job for me though.
 

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Discussion Starter · #11 ·
Thanks for the replys guys . Devo , Bonneville head =2 carbs . I will try jetting down i have some 190's. I wonder if a phelonic spacer on both sides would do well I have found they seal good even without o-rings in the carbs because they mash down a bit without overtightening. I put my hands over the velo stack when it was running there was no big difference maybe that a sign that there is a leak. I didnt try to stall it by covering completely I will try that today. That would tell me there is a leak somewhere if i cover both completely and it still runs.
 

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Discussion Starter · #12 ·
Devo maybe you can get me closer . I swapped the 932 for good runing 930's and its exactly the same. Can't find aleak with carb spray. Where do you have your mixture screws and needle position set at? Maybe this will give me starting point cause i have been through the basics all more than once. Gaskets and.orings and the gammit.
 
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