Triumph 675 Forums banner
21 - 25 of 25 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter · #21 ·
Engine and rear end work

Sorry for taking a while to get back to this. I had a dirt biking injury that ended my season after the race I posted about above (although I did race a hare scramble at the end of the season). I'm back on this and am pumped up about roadracing again. Here are some updates.

I picked up a 2012 engine with supposedly 7k miles on it. Appears to be in good condition. I have taken 0.010" off the head and found a kit 0.60mm gasket. I will be reassembling soon, lapping the valves and putting in new OEM springs, retainers, collets, stem seals, some other stuff I'm probably forgetting. I got the UKRS spring kit which has Suzuki springs for one side with spacers (forget if that's intake or exhaust), OEM on the other. Got an APE manual tensioner, but cam chain looks good. I have a dude straight piping the headers now. Will be using the 09-12 intake stacks, K&N filter, and getting it dyno tuned. I'm thinking about exhaust port matching, will have to see what the new gaskets look like. The problem I see is that if you were to put the gaskets in place, tighten down the manifold enough to make a mark in them, and take the manifold off, if you grind off the excess gasket and port material for a smooth transition, when you tighten everything back down for good how do you know the gaskets don't shift? If you have to replace the gaskets what if the material you took off the head was not good for where the new gaskets want to sit? Probably overthinking this. I don't know much about porting and polishing so I'm not going to attempt that this time. A project for another time, another motor (or maybe not).

Got a set of R6 calipers, spacers, some CL C59 pads, an Accossato 19mm master, and Galfer lines. Going to get this done after the motor is back in.

Regarding the rear end. If you recall I was having issues with a bumpy entrance to the straight, while hard on throttle. There are two camps for spring rates, some say somewhere around 12 kg/mm for me at 200 lb geared up, others say somewhere around 10 kg/mm. I had been running an 11.6 but ended up dropping the preload incrementally down to 6mm. So I just picked up a 10 and will be putting that on for testing. That way I can get closer to 10mm preload and the spring force won't ramp up so quick, that may be my problem. Hoping to still get around 10 or 15mm free (static) sag.

Another thing I was considering was the "non-linear" linkage everyone is going on about on these bikes. People say it's so non-linear sag numbers are not standard, and the ramp up so quick that they cause handling issues on track especially. I thought maybe that was part of my problem. So I just took the spring off, put shock back on, and measured the rear axle position (distance to a subframe point) and shock shaft length all the way from full extension to compressed up to well into the bump stop. I stopped measuring when the frame kept lifting up as I was lifting the axle (my engine is out, I could get more data when the engine is back in).

The results are attached, it appears to me that the linkage is VERY linear. I assume the "curve" will change as the shock is getting close to bottoming but I was not able to measure this - in other words maybe it becomes non-linear further in the stroke, but I measured up until there was only around 10mm left in the shock and the tire may hit by then anyway. To be specific about my particular measurements, there are 14 data points, I have a Penske double adjust shock as short as it will go, this is to get me back to just about stock ride height (2mm higher) after upping the swingarm pivot position. These results are important because I was considering dropping the rear a bit more to get more trail, but I did not want to just get deeper into the linkage's non-linear region because that would make my bump absorption problem worse. From my data it looks like this will not be the case! This could be because my shock is short, maybe if I were to lengthen the shock adjuster and decrease the dogbone length to reach the same ride height but put the linkage in a different part of its stroke, the data might come out differently. I have an adjustable link so I could do this if I have time and anyone else is interested.
 

Attachments

·
Race Team Sponsor
Joined
·
101 Posts
Keep the information flowing, I've got the same year bike I'm hoping to get on the track this year.
 

·
Registered
Joined
·
25 Posts
Discussion Starter · #24 ·
Have been riding a lot this year. Other than a bunch of track days I've raced two rounds at Arroyo Seco Raceway in southern NM with ASMA, one round at High Plains Raceway near Denver with MRA, and just learned a new track in Pueblo, CO this past weekend to prepare for races there with MRA in a few weeks.

I've been finishing on the podium for amateur races with ASMA, won 4 of 5 last round, and did pretty well at HPR with my best finish being 2nd in thunderbike.

The bike is dialed and I think I have outlined all the mods to get here pretty well in other posts. I did try a few fork positions recently and results were that I cannot steer the bike with fork caps flush to triples but at 3mm exposed (including cap) it is a good balance of steering ease and stability. Not sure if I did update on this, but the 9.8 kg/mm shock spring with 10mm preload is what I've settled on.

Just scored a set of attack triples at the track last week for a good price. Ordered the #2 offsets for 28mm, and a bracket to try to mount the hyperpro damper onto the fork leg while still using the stock mount under the steering head. I don't have time to test so I am not sure if I will make these changes before the races in 2 weeks or not. Wonder if I could keep my geometry and have the 28mm offset work well, or if it will be necessary to change fork position which will take some testing time. Blew a fork seal so might be the time to change the triples while the forks are out but we'll see. I also have a topout spring for the penske shock and will put that in sometime soon also.

Video of the 1 of 5 races I did not win at ASMA in round 2, but did finish 2nd. Bet you can tell why I did not win!

 

·
Registered
Joined
·
107 Posts
I know this is an older thread but I have decided to take my 2006 and slowly convert it into a bike to control ride trackdays and perhaps do a race or two. Appreciate all the info you've provided, especially regarding the geometry setup. Biggest thing I've noticed on the bike in stock trim is it feels very twitchy when going into corners and the taller profile isn't helping the feeling I want. Started some adjustments at the fork position in the caps and going to see where that gets me.
 
21 - 25 of 25 Posts
Top