I am rebuilding my 1976 TR7 and want to increase the mid range power. Have bought 8.75.1 hepolite pistons and a late 650 ex cam with the "spitfire" profile, will be using std exhaust system with 42T rear & 21T front sprockets. The bike is ridden between 2600 and 4400 and never over 5500, am considering using a 32mm Concentric instead of the 30mm and can't find any tuning info for 32mm carb on single TR7 head anyone got any info or suggestions on my mods and been told 75% balance factor is better for the street than 85%. Steve
What sort of lift and timing on the spitfire ex cam ?
The std cams out of the '68 or '69 650's [either T120 or TR6] are bloody good road cams, if you weigh more than 70 kg the bike will probably be overgeared with the 21T gearbox sprocket, I weigh 100kg and my TR6 was overgeared at 20T, an ordinary circumstances rev limit of 5000 is quite a good idea but do not try to get the bike to roar up long hills at 3500 RPM it will not happen, gear it to pull 70 MPH @ approx 4200 RPM and it will be a much livelier bike and last longer than if you load it up at lower revs. I agree with Panic re carb size, also be aware that the TR6 uses a 3 1/2 slide as opposed to the 3 of the Bonny, if you buy an off the shelf 930 AMAL check that first. Better still speak to Jeff Skillen on 0249323231, he is in Maitland and does magic work on Amals at a fraction of the cost of buying a new body and slide. Jeff fits Mikuni slides and also trues up the mounting flange relative to the carb bore to eliminate cylinder bias, a std new production 930 will need a replacement slide at about 3K miles, they are pretty ordinary but fitting anything else to a TR6 is not worth trying as the weirdo manifold supplied with Mikuni conversions, and the aircleaner, fail to impress [as does the price] Regards Tiger
I would be interested speak further
1969 TR6R 7.62 x 51 is not a maths puzzle.
Re: TR7-T140 mods and cam timing info#90431 04/11/0612:19 pm04/11/0612:19 pm
Thanks for the info, I fitted a 32mm some years ago (I've owned the bike since 77) and with non standard mufflers 310 main with No1 needle and 3.5 cutaway the bike went great but there was something amiss with the carb. It would run great and then for no reason wouldn't idle at all, checked everthing numerous times float level, fitted viton, stripped and blew out the body, checked the flange for truth and after a while gave up and replaced it with the 30mm. Figered that there was something wrong with the casting of the 32mm. The late BSA big valve super rockets went hard they had 1' 5/32 monoblocks that's were I got the idea of fitting the larger 32mm carb. The "spitfire" cam uses the profile from the BSA cam suppost to give the TR7-T140 a good lift in performance, the profile I'm told was the same as 1969-1970 T120. I weigh 75kg and the gearing seems fine but I hear what you saying. Anyone fiddled with the balance factor at 75% opposed to the 85%?
Re: TR7-T140 mods and cam timing info#90432 04/11/069:07 pm04/11/069:07 pm
Thanks Tiger the cam's part No is 70-9989 and the timing is: ex opens 55 and closes 34. I take it that the ex tappet clearence would be 004' instead of the 006'in the STD TR7-T140 ex cam. Just on the timing the 750's have the timing specified in 19" btdc and ex closes at tdc 13" can any one explain this method? I take it that it means lock the crank with the t.d.c.tool to establish tdc on a degree wheel then wind the crank back 19" and the inlet should be just opening with the tappets set at 020' My problem is I have always checked timing in degrees how do I convert to inches on my timing wheel sorry for the ignorance as the answer is probably very simple. If anyone can enlighten me on this method it would be appreiceated as I think that I will have to use the 2 methods one for the TR7's inlet and degrees for the 70 T120 ex cam, help please!
Re: TR7-T140 mods and cam timing info#90433 04/12/0612:09 am04/12/0612:09 am
"Figered that there was something wrong with the casting of the 32mm" ------------------------------------ Very rarley will blowing out the pilot jet, located under the pilot air screw, clean it. Most times you have to actually get a #78 drill (.016"), mount it in a small brass tube, and physically clean out the jet.
If the pilot jet is blocked. or partially blocked, it will make tuning the carburetor near impossible.
In my experience the stock 85% works well in a stock bike (frame, front end, etc.). When you get an opinion about a balance factor be sure to understand what they are talking about. 75% of what, as my balancer is quick to respond. Everyone needs to be talking about the same thing. There are some strange balance theories out there. I am not saying that you might not be happy with a 75% factor, but be sure your "expert" is talking the same language as your balancer.
In my opinion there are only two cheap, and reasonably reliable ways to guarantee improved performance (well, really three - loose weight): more compression (which is out these days becasue of the gas) and more cubic inches. You spend money on compression and cubic inches and you can almost guarantee more performance.
Anything else is time consuming, rarely done on the first pass and very expensive if you expect any real gains. And installing that big bump stick with a large hole carburetor might actually make your scoot slower where you are looking for improvement. Guys that are succesfull at this stuff aren't called "tuners" for no reason at all.
Access to a dyno will make the process easier.
I will tell you that the cam timing suggested on the manufacture's cam slip will rarely be the cam timing that will produce real horse power where you neeed it. The carburettor size you guess at, will rarely be the size that gives you real horse power and where YOU want it in the rev range. And big valves in a stock, or near stock, Triumph can be a real loser.
I can go on about valve size, intake length and porting; exhaust port height, cross section; exhaust pipe diameter and length; muffler design and restriction; etc.; etc.; etc..
A Triumph T120 exhaust cam (E3134 profile) open 58 degrees bdc closes 34 degrees atdc measured at .020" lift .004" running clearance 102.5 degree lobe center.
Or better yet, use the stock timing marks for both camshafts to begin with. What ever you start with, chances are the cam timing will be different when you find the kind of horsepower you are looking for with your set-up.
Re: TR7-T140 mods and cam timing info#90434 04/12/068:27 pm04/12/068:27 pm
It's hard to successfully tune a good bike. A Triumph Thunderbird fitted with 9/1 pistons, baffle-less exhausts and E3134 cams, or other sporty cams will be a better bike than standard, in most ways that appeal to me. It will be faster all round, because it was under-tuned to start with.
Further tuning, or tuning a faster bike, like a 1969 Bonnie, is not so simple. The trade-offs start to rear their ugly head. Lengthy experiments with exhaust and inlet tract length might get you more midrange at the expense of top end.
Amateur Loctite enthusiast.
Re: TR7-T140 mods and cam timing info#90435 04/12/069:50 pm04/12/069:50 pm
Thanks to all of you for your comments, the bike is already stripped and ready to re-assemble I bought the Hepolite pistons which I'm told are 8.75-1 (old stock not TRW) and on examining the new rod bolts and nuts the bolts are slightly shorter and the locknuts are not the same as orig but appear heavier as will be the +20 pistons. I am going to balance the crank myself and will take your advice on the 85% factor as the bike is in a stock frame forks etc and will be used for road use and not thrashed. The 85% seems to be the most popular choice by people who have tried it. I'll try the 70-9989 cam with the std timing marks and go from there but on the wieght of everyone's comments might leave the 30mm carb on for now and sort that out later. Just one thing that no one touched on the cam timing method using TDC and the amount of lift in inches. I take it after more reading that you lock the crank in TDC with the tdc tool and then wind back the inlet cam then bring it forward (opening) until the lift in inches is achieved using a dial indicator at the rocker with 0" clearence. Then the ex is checked by rotating it backwards (closing)to the correct seting is achieved. Then check the othe side the same way. Anyone used this method?
Re: TR7-T140 mods and cam timing info#90436 04/12/0611:44 pm04/12/0611:44 pm
Now that we have deflated the ballon think about what changing the closing time of the exhaust valve does. You can either do this by designing a cam with a later or earleir closing time or take the cam you have and change the lobe center timing figure.
There is so much you can tell by looking at the external parts of a motorcycle motor. The tuner cannot hide the length and type of exhaust system or the size carb being used or the inlet track length. I gives you a part of the puzzle. All you need to do then is put all of the rest of the bits together.
Because people naturally want you to know they know more than you do, they will often tell you the truth about many things they did inside the motor : cam, valve size, etc. It's up to you and the dyno to fill in the blanks.
But one thing that I have never got out of someone that found some real horsepower out of these motors is the cam timing (lobe center) they are using. If they told me I would probably not believe them.
The wonderful thing about Triumphs is you can make lobe center changes on the exhaust without changing the intake. A luxuary Norton owners do not have.
Now I am told by Leo Goff, that for a given set-up you only have about a 2 degree window to work with. Either side of this "sweet spot" the power falls off significantly. Make changes and the window will/can move.
So think about the closing figures of you exhaust cam and how (and why) that can help you have more mid-range power.
If i am getting into trouble hear Panic, come to my aid... john who isn't so cranky and just had a Krispy Kream jelly doughnut.
Re: TR7-T140 mods and cam timing info#90437 04/12/0611:47 pm04/12/0611:47 pm
Thanks John for your comments one other thing just cam up. I read a thread you replied to about correct bearings for Triumphs and you gave some fantastic info so much so that I printed it out for future quick reference. My question is I just examined the bearings I have and found the drive side RHP with a bronze cage that is marked "MRJA 1'1/8 MA" on the packet and the inner bearing is marked "RHP then MRJ1 1/8 A" but no other letters indicating clearance. Is this bearing correct for a TR7 750 1976 engine No AN66999. The other side is a 6306 FAG C3 also the torrington needles I have for the top gear are marked S then opposite B-1314. The orig ones were marked N then B-1314. The S ones feel like they have more clearence when the shaft is inserted. Can you or anyone help as I don't want to reassemble the gear box with the wrong clearence bearings.
Re: TR7-T140 mods and cam timing info#90439 04/13/061:40 pm04/13/061:40 pm
The bearing used in the drive side of a 750 twin is a MRJA1 1/8 C2. Because it is not in a "normal" condition both the box and the bearing would indicate that it was C2. When I was a lad, the pre-fit internal clearance was indicated by small pollished circles on the side of the bearing race. Thus you will read in old literature about one spot, two spot, three spot, etc. bearings. What they were refering to was the amount of pre-fit internal clearance.
The "spot" reference gave way to the "C" marking late in the 20th century. A bearing that does not have what is called "normal," or CN, pre-fit internal clearance will be clearly marked with one of the "C" markings. A bearing without any "C" markings would be considered CN, or normal.
The bearing you have is a MRJA1 1/8 CN. This bearing is standard for the drive side of BSA A50, BSA A65, and Triumph 650 twins.
Now a wise man would ask when did Triumph change from CN on the drive side to C2? Well I asked Brian Jones just that question. Brian was the engineer in the period of the worker's co-operative. He did confirm the change, but didn't recall when he did it.
I have worked with Keith Martin, and others who do a lot of these engines over the past 10 years. The best we can come up with is the CN was used right up to the worker's sit in. So the CN would be used right through the early 1976 models assembled during the strike. The consensus of opinion is the C2 condition was introduced in the late 1976 models assembled by the newly formed worker's co-operative.
There are those who claim triumph always used a C2 condition. There is plenty of evidence that this did not happen. Those familiar with the BSA A65 realize that in the early 70's they changed the condition of their drive side bearing. Up until that point they used a MRJ 1 1/8" bearing with an inner race of their own specification. The inner race had a smaller o.d. than the standard bearing. It utilized a small tin cup to hold the spacing shims. In an effort to save money they standardized on the Triumph bearing, which required them to use a larger tin cup. Yes, the BSA MRJA 1 1/8 was in a CN condition.
More than you need to know, but where else can I talk about this stuff. My dog won't listen...
Re: TR7-T140 mods and cam timing info#90440 04/13/063:39 pm04/13/063:39 pm
more about the bearing issues.. my dog doesent listen to.
one thing to consider is to change the timing metric ball bearing to a roller bearing..Why??
well.. up to 1971 they had a non metric timing bearing on the 650 with the name MJL1/8JC3 this bearing was a very tuff bearing and worked just fine on the 650 in 1971 they changed the timing bearing to a metric bearing 6306 ,this 6306 bearing was mutch weaker than the non metric bearing(MJL1) with smaller balls etc,but it still worked fine on the 650...But.. than 1973 the first T140 750 was born and the trubble started..the timing bearing was breaking because off the increased power on the 750 so they detuned the exhoust cam to prevent the bearing to fail..
but they fixed the problem but i dont know what year?, the solution was a nup roller bearing NUP306ETC3..this bearing looks realy tuff and if i was you i should change the 6306 bearing to the NUP306ETC3 roller bearing
If you look at the late 650 bearing MJL1/8JC3 beside the metric 6306 bearing you understand why the 6306 dident hold together a mutch weaker bearing..=)
Re: TR7-T140 mods and cam timing info#90441 04/13/0611:42 pm04/13/0611:42 pm
How can I thank you guys for the invaluable info! I have seen the NUP bearings out of the later models and read somewere a lot of beers ago on the conversion for the earlier ball models. I seem to remember the article said that you had to change the clamping washer that sits between the pinion gear. I checked the part numbers between the 76 mod and an 82 mod parts cat and the part no's are the same. Have I answered my own question is it a simple matter of just changing the 6306/C3 for a NUP 306ET C3 and thats it? Also while on the subject of bearings the Torrington bearings used inside top gear, the ones I removed were stamped with a "N" on one side then the number B-1314 on the other but the replacments I have are spamped "S" then the number on the opposite side is this a clearance letter (N for normal S for slack ha ha ) as the new ones feel a bit more "sloppy" on the shaft after pressing them into the gear? I can't find any Torrington info on the net.