Need Help with 73 Front End Swap

+1 grind press swap the stems, I have done it a couple of times, or use an XS750 "standard" fork AFAIK it is plug and play but the tubes are a bit longer (1"?) No matter how big the fork IMHO the early frames are still "whippy" compared to the better braced late frames.
So as always when modding, the whole bike should be considered in your "goals"

Back in the day road racing my CB900F at Road America a guy had an H2 750 that really made some horsepower, he had grafted some big wing? front end on the notoriously flexible H2 frame, I'd pass him every corner he'd take it back every straight. He finally tried to match me through the corner, I last saw him headed out into the woods riding a tank slapper.
Old thread i know but i just acquired a 1970 xs1 and i am looking at putting a later probably 80s fork on it what is everyone talking about machining down to fit in the triple clamp?
 
Early frames have a neck that is about 1/2" shorter, later stems are too long without some mods or spacers.
 
Early frames have a neck that is about 1/2" shorter, later stems are too long without some mods or spacers.
Is there a good source for spacers or someone on here who has some plans or something for mods. I have gathered that they are different. I am kinda torn i am building a cafe racer and i am looking at a way to get disc brakes up front.
 
I'd consider a plug 'n play xs750 Standard front end swap. 36 mm diameter but a little longer, run the inch or so extra length up and have a place for clip ons. Spindle length the same? Smaller diameter brake rotor for better front wheel profile, heck, run dual discs. Again, spindle length the same? Makes the difference. Headlight adjuster mount is a little different and the risers stand up a little more proud.
 
I have a set of forks from an XS1100 standard. The upper tubes are 37 mm. The Stem from the where lower bearing seats to the top of the stem is 8 5/16 inches.
I have a set of 75 34 mm forks and the stem is 8 7/8 inch measured the same way.
Does anyone have an early stem to measure?
The XS1100 stem has tapered roller bearings on it. I would think they would fit in the races that come with the tapered roller set for the XS650. So I think they would bolt on to the early bikes by just using the races from the XS650 kit.
There is one difference that may or may not make it workable is the offset. On the XS650 trees there is a just under 2 inch offset from the center line of the fork tubes back to the center of the stem. On the XS1100 trees the offset is 1 3/8 inch.
This will increase the trail by 5/8 inch. The stock trail on the XS650 is 3.9 inches, adding 5/8 inch makes it 4.525. This may make the bike handle a bit differently. I think a bit harder to turn, a bit more stable at speeds.
I plan at some time in the future to try the XS1100 fork on my 75.
The larger tube diameter makes the forks stiffer. As with any tube the larger the diameter the stiffer it will be. With forks this helps keep the front wheel pointed where it needs to be. A smaller fork tube flexes more during turns, this allows the front wheel to not turn as far as handle bar inputs. A larger tube diameter lessens this flex.
Leo

Hi Leo,
I recently sold my XS11SG so can't measure it, are the XS650 & XS1100 forks the same length?
When prepping my XS11SG for sidecar work I swapped the longer XS1100 Standard 'trees into it's forks
to reduce trail so it steered lighter. Are you sure the 1-3/8" offset was for XS11 Standard forks, not XS11 Special's?
 
Alrighty....
Measuring the spindle that was pulled from a Standard model xs750, thinking the donor year was '77.
Overall length is 232 mm. Keep in mind that this had its weld ground off so there may be a mm or two in discrepancy.
The business length, from where it was inserted into the lower triple and then to the top is 210 mm. This is a best guesstimate by looking for wear or insertion marks.

Now, what are the early model xs650 spindle measurements?

I'm going to add here that the '83 xs650 lower triple has a 3 mm platform that sits above the overall plain of the lower triple......where the lower race sets upon. The xs750 lower triple didn't have that platform, it was flat overall. Something to consider whilst measuring.
 
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