changing a tiger into a bonneville/best electronic ign.? - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 108 (permalink) Old 10-22-2019, 09:43 PM Thread Starter
Grand Prix 125
Main Motorcycle: '78 Triumph Tiger 750 TR7
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changing a tiger into a bonneville/best electronic ign.?

recently I purchased a '78 triumph tr7v tiger(t140 750cc) & have a few questions. I want to covert my single amal to a dual mikuni, who makes a intake manifold for this? it's my understanding that it can't be done with my type of head using mikunis, that I might have to use different carbs that are narrower than the mikunis. also i'm converting it to electronic ignition, i'd like pros & cons on boyer v.s. pazon. thanks for any input you can give me.
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post #2 of 108 (permalink) Old 10-22-2019, 10:25 PM
SuperBike
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IMHO opinion keep the single carb. You are giving up very little in performance and much easier to tune and maintain. I have 5 bikes with Pazon Surefires.
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Htown16, Houston, Texas
1978 T140E Bonneville, 1974 Trident, 1972 Commando, 1971 Commando
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post #3 of 108 (permalink) Old 10-22-2019, 11:05 PM Thread Starter
Grand Prix 125
Main Motorcycle: '78 Triumph Tiger 750 TR7
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Thumbs down hating my amal

thanks htown, but if I stay with a single carb it's not going to be the amal. I can't think of 1 friend or neighbor that I have that would appreciate my bike leaving a a puddle of fuel on there drive after visiting, plus i'm still having a tough time trying to figure out how much to tickle it to get it started as I live in Ohio & the weather keeps changing 10-20 degrees every other day which seems to make a big difference on starting procedure. not to mention it dripping all over my cases. but thanks for the advice on ignitions.
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post #4 of 108 (permalink) Old 10-22-2019, 11:14 PM
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No need for a 'puddle of fuel'....all you do is tickle it till fuel shows. Once you have fuel the float bowl is full, no need to keep tickling, it won't do anything except waste it.

If you are set on ditching the Concentric, consider an Amal 1.5 or MkII. No tickler and basically a bolt on job.

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post #5 of 108 (permalink) Old 10-22-2019, 11:39 PM
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i vote for the mikunis. i gave up on messing with concentrics years ago, and now if they're not right i put the mikunis on as a first step. easy to tune, precise, don't wear out.

you have the parallel straight port 10-bolt head, and mikunis are pretty wide. the old 650/750 splayed port heads will fit them. there are still conversions for the TR6 to T120 configuration around, but i don't know if they will fit the TR7. swapping to the old 650/750 nine or nine and a half-bolt heads would do it, but you'd have to swap jugs, pistons, and heads.

but you can find a way. look at these:



https://www.mikunioz.com/shop/mikuni...v=7516fd43adaa

the bolt centres are 51 instead of 50mm, but you can file them and use allen heads to fit on the bike. the mikunis will fit right on. but you will still have sidecover issues.

alternatively, any straight two-inch spigot will work on the head and a piece of bent radiator hose at the right shape and angle will let you put the carbs wherever you want them. this is cheap and easy.
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Last edited by speedrattle; 10-22-2019 at 11:45 PM.
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post #6 of 108 (permalink) Old 10-23-2019, 12:55 AM Thread Starter
Grand Prix 125
Main Motorcycle: '78 Triumph Tiger 750 TR7
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thanks speedrattle I like how you think, not dissing the rest of you all gave great advice & much appreciated.
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post #7 of 108 (permalink) Old 10-23-2019, 02:21 AM
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Hi tiger78, Interesting.... Tigers are very good starting bikes. I feel a little easier than Bonnies. However, properly tuned with a good carb & battery all these bikes are good starters. Generally the first kick.

I understand Ohio can be much colder than where I live. I've started my bike at 22f a few times. Always first kick. Many times in upper 20s to lower 30s. Never fails. Lots of times from 40s-60 in garage all winter. I ride all year, did a ride in mild snow last winter.

My feeling is your bike is out of tune. Or.... it's worn out. My carb finally wore out & caused dying at idle & just above idle. Still started well though.

On club rides a few guys have Mikuni on Bonnies or Nortons. I don't see them starting any better. When smoking hot it seems they start worse. Sometimes much worse. At least with Amal concentric you can tickle it hot & give full throttle. It starts first kick then.

Amal Premier Tiger 750 carbs are not so easy to get with slides, jets, banjo, top you want. I emailed Amal direct. Email Phil & tell him what you want. You'll pay by pay pal. Will arrive in 1.5-2weeks. Even if on back order, he can assemble one just for you. Aprox $200 US with shipping. Depending on dollar/Pound values.
They built to my specs. I wanted #3 slide for California fuel. Also make sure you get .019 idle jet. NOT .017 like the original had!! The new Premier is different internally & needs .019. Amal now makes a .1065 needle jet. Slightly larger than normal. I'd recommend that. Needle clip on bottom groove. I'm using 280 main jet & it's working quite well for me. For Ohio fuel I'd probably stay with 3.5 slide. What do you have now & how does it run 25-40 mph?

Always run highest octane fuel they sell even if it contains ethanol.

My bike starts & runs so good I can't believe it after installing new Premier. I made sure all else was perfect before getting new carb.

I think you will find well tuned your Tiger 750 will run with a Bonnie 650 no problem & also run with T140 no problem.

I reworked my AAU to change advance curve. The electronic ignition come with a very desirable advance curve.

Your original points AAU is full advance at 2000rpm. Boyer I know from testing in real life gets full advance 3500 rpm in a liner fashion as rpm increases. That substantially reduces ping. I've not personally tested Pazon, but I have friends that use them & find the advance curve is similar. So either will work very good. I'd probably get the one that is the least sensitive to low voltage.

One thing is points will start & run with a low or dead battery. Points allows bike to at least run even if not properly with a faulty charging system.

It is stupid to not have a perfect charging system & battery. It just makes the bike start & work properly. Electronic ignition is very voltage sensitive. You MUST!! have a perfect charging system & battery with electronic ignition.

I wonder if some of your current woes could possibly be related to low voltage?

What is the float level on your current concentric? If... this is the original carb the level is not .080" below gasket surface, but level with surface or just above with float horizontal. The true way to check is the liquid level on bowl. If want I can repost the Amal float level sheet. You must use a stayup float & viton tip alloy needle. Remember slide/bore wear cannot be overcome. Don't sleeve. Get new Premier.

All the rest of motor, valve adjustment, point gap, clean points, ignition timing, compression must be checked & made good.

So have lots to think about. I don't know if you've already gone over all these other items. If not I'm afraid the Mikuni is possibly going to be no better. I stand by the Amal Premier. Properly installed they start & run really, really well.

Don
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Last edited by TR7RVMan; 10-23-2019 at 02:24 AM. Reason: changed sentence
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post #8 of 108 (permalink) Old 10-23-2019, 04:24 AM
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Since you asked for advise, Don has it pretty much on the nail. You have purchased a vintage bike that is not running right, what have you done to try and fix this problem?

Have you checked compression?
Have you checked the charging system and battery?
Have you checked the ignition timing?
Is the carb bore worn or distorted?
Is the carb mounting flange distorted?
Has the needle jet been replaced recently?
Has the pilot jet been cleaned?

I don't wish to sound harsh but you are at risk of falling into the standard trap of chucking a small fortune at aftermarket parts thinking they will be the fix for all your woes only to wind up skint, disappointed and disheartened.

Rod

Last edited by Redmoggy; 10-23-2019 at 04:35 AM.
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post #9 of 108 (permalink) Old 10-23-2019, 09:52 AM
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I've had several Pazon failures.. Great warranty but if you need to return them to NZ from the USA, it costs for postage and takes a month for turn around..It's my opinion than the majority of running issues with old Brit Bikes are due to poor tuning and improper riding style. If the bike is stock, carb tuning on an Amal is easy,use recomended jetting, bolt on, ride..If it runs crappy ,that's when it gets interesting..

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post #10 of 108 (permalink) Old 10-23-2019, 10:01 AM
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I ride my Trident quite often with my friend on his 69 TR6 with Monoblock.
This bike holds 90 mph without any problems seeping gas in the same time, quite differently to my Trident. I believe it's max speed is over 100 mph and I don't think TR7 would be any worse when in good fettle. Don't see any reason to go to double carbs.
Also wouldn't go to Mikuni, when Amal Premier looks correct and doesn't wear for a long time.
Longer tickler keeps your fingers clean as well.
You don't needs lots of tickling when you start with choke on.
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